A Study on the Solidification Behaviour of Al-Cr-La Alloys in the Aluminium-Rich Region

A Study on the Solidification Behaviour of Al-Cr-La Alloys in the Aluminium-Rich Region | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article A Study on the Solidification Behaviour of Al-Cr-La Alloys in the Aluminium-Rich Region Tilen Balaško, Jožef Medved, Simona Delsante This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7796354/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract This study examines the solidification behaviour of Al-Cr-La alloys, reflecting the increasing use of rare-earth elements to enhance the properties of aluminium alloys. The research aims to determine how the new ternary phase Al 20 Cr 2 La, formed by the addition of La, influences the solidification process. This fundamental understanding is essential before these alloys can be developed for high-performance applications. Ten alloys with varying Cr and La contents were produced using an arc melter. After annealing, their solidification and microstructure were analysed using DSC and SEM. In alloys with higher Cr content, solidification begins with the Al 45 Cr 7 phase, followed by the ternary Al 20 Cr 2 La phase, then (Al), and finally a mixture of (Al) + Al 11 La 3 . Thus, these samples (A–E) exhibit four phases: Al 45 Cr 7 , Al 20 Cr 2 La, (Al), and Al 11 La 3 . (Al) is present in the matrix and mixed with Al 11 La 3 , while the ternary Al 20 Cr 2 La phase is observed around the binary Al 45 Cr 7 phase. In samples F–J, solidification also begins with the binary Al 45 Cr 7 phase, followed by the ternary Al 20 Cr 2 La phase and (Al), and finally the (Al) + Al 11 La 3 mixture. In this case, the microstructure of samples with increased La content (F–J) consists of the ternary Al 20 Cr 2 La phase, the (Al) + Al 11 La 3 mixture, and an (Al) matrix. Al-Cr-La solidification DSC microstructure Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 INTRODUCTION The ternary Al-Cr-La system still contains many unknowns. This system has attracted attention because aluminium alloys are now frequently alloyed with rare earth elements (REE) to achieve improved mechanical and physical properties. Other researchers [ 1 – 9 ] have shown that the addition of La enhances the mechanical and corrosion properties, partly due to the refinement of (Al) crystal grains and a reduction in secondary dendrite arm spacing (SDAS) [ 1 – 3 , 10 ]. Studies indicate that the addition of La in binary and ternary systems not only refines (Al) grains but also promotes the precipitation of Mg 2 Si [ 9 ] and modifies the Al 13 Fe 4 [ 8 ], Mg 2 Si [ 11 , 12 ] and β-AlFeSi [ 13 ] phases. Furthermore, in high-strength 7xxx-series aluminium alloys with added Cr, La additions have been found to modify the Al 45 Cr 7 phase and form the ternary Al 20 Cr 2 La phase [ 12 ]. Given these positive effects of La additions to aluminium alloys, this influences the growth potential of demand for such alloys, as previously mentioned [ 14 ]. Considering that 7xxx series aluminium alloys are widely used in transportation [ 15 – 22 ], their improved mechanical properties through La additions offer several advantages. Firstly, these improved properties could broaden their applications in the transport industry and potentially enable them to replace steel in certain structural components. Secondly, aluminium alloys possess an excellent strength-to-mass ratio due to their lower density compared to steels. Consequently, higher mechanical properties can result in reduced mass in cars, lorries, trains, and aeroplanes. Reduced mass directly leads to lower fuel consumption and a smaller carbon footprint [ 23 – 25 ]. For example, car manufacturers have already committed to reducing average carbon emissions by 37.5% between 2021 and 2030 [ 26 ]. As a result, the average Al content in passenger cars is projected to increase from 121 kg in 2006 to 256 kg in 2030 (net mass) [ 27 , 28 ], with the overall use of aluminium alloys in transport expected to rise by 55% from 2017 to 2030 [ 28 ]. In order to better understand the effects of La addition to Cr-containing alloys, this study examines the solidification behaviour and phase evolution of alloys in the Al-Cr-La ternary system, particularly in the aluminium-rich corner. Differential scanning calorimetry (DSC) was used to evaluate transformation temperatures and clarify the solidification path. Microstructural analyses were performed using scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDXS) analysis to investigate phase evolution. EXPERIMENTAL WORK Materials The alloys were produced in a vacuum arc melting system (MTI SP-MSM208) using a non-consumable tungsten electrode and a water-cooled copper furnace. Pure Al (99.99 mass%), Cr (99.99 mass%) and La (99.99 mass%) were used as starting materials. A high-purity Ar atmosphere (Ar 6.0, 99.9999%) was maintained and further purified by melting a Ti getter (99.7 mass%). Before introducing the Ar, the melting chamber was evacuated, and the residual pressure was monitored with a vacuum gauge. To ensure chemical homogeneity, the alloys were remelted four times. After production, homogenisation was carried out in a Xiamen Tmax Battery Equipments Limited SK2-4-12TPB3 tube furnace under an inert Ar (Ar 5.0, 99.999%) atmosphere. To further purify the inert gas and prevent oxidation, Mg crisps (99.99 mass%) were added to the tube as an oxygen carrier. The samples were stored in Al 2 O 3 crucibles prior to homogenisation, which was performed at 600°C for 600 hours. After homogenisation, the samples were quenched in ice-cold water to obtain the equilibrium structure. The chemical composition (Table 1 ) was measured with the OES ARL iSpark 8860. Table 1 Chemical composition of the investigated alloys in at% Sample at% Al Cr La A 98.67 1.3 0.03 B 98.75 1.1 0.05 C 98.70 1.20 0.10 D 99.07 0.76 0.17 E 99.09 0.83 0.08 F 99.57 0.03 0.40 G 99.50 0.20 0.30 H 99.30 0.30 0.40 I 98.80 0.70 0.50 J 97.00 2.00 1.00 Differential scanning calorimetry (DSC) Samples measuring approximately 3.5 x 3.5 x 2.0 mm (± 0.2 mm) and with a mass between 30 and 50 mg were prepared from the alloys for differential scanning calorimetry (DSC) analysis. The solidification path was examined using a NETZSCH STA 449 C Jupiter instrument. The samples were heated to 1100°C at 10 K min − 1 and cooled to room temperature at the same rate, with the furnace maintained under a protective argon atmosphere during the analysis. Empty Al 2 O 3 crucibles served as the reference. Only the cooling curves were used for analysis, as the study focused on solidification. The DSC analysis determined the transformation temperatures of the solidification path, with phase transformation temperatures evaluated according to the recommendations of Boettinger et al. [ 29 ]. DSC analysis provides highly accurate results for studying the solidification process of metals and alloys, as repeatedly reported in previous studies [ 30 – 31 ]. Metallographic analyses Before metallographic analysis, the samples were ground with silicon carbide paper and polished with a diamond–water suspension on fabric discs. Optical microscopy was performed using a Leica DM4000 M optical microscope equipped with an AxioCam ERc 5s high-resolution digital camera. The microstructure was then analysed with a Zeiss EVO 40 SEM equipped with a PentaFET EDXS detector (Oxford Instruments) using the backscattered electron (BSE) imaging mode. RESULTS AND DISCUSSION The results of the DSC analysis are shown for the temperature range between 550°C and 850°C, during which the solidification process was analysed. The figures in this section were selected based on the different sample compositions, and only the most representative results are presented. DSC analysis The DSC analysis of the samples with increased Cr content (A–E) revealed two peaks for sample A (Table 2 and Fig. 1 a) and 3 peaks for samples B–E (Table 2 and supplementary), although for these samples the third peak appears only as a “shoulder” on the low-temperature big peak. It was expected that the Al 45 Cr 7 binary phase (also known as Al 7 Cr and Al 13 Cr 2 ) [ 32 ] would begin to solidify first, as the Al–Cr binary phase diagram shows a higher melting point, indicating that this phase is typically present in molten Al at these temperatures. Indeed, this property is used industrially to refine the cast grain structure and prevent excessive growth of (Al) crystal grains during heat treatment [ 33 ]. Thus, while the first peak in samples A–E indicates the solidification of Al 45 Cr 7 , the second peak corresponds to the solidification of the LaCr 2 Al 20 phase and a mixture of Al 45 Cr 7 + (Al). The third, unexpected peak was confirmed by subsequent microstructure analysis (the microstructure of all mentioned samples also consists of a mixture of (Al) + Al 11 La 3 ), indicating that the third peak (“shoulder”) corresponds to the solidification of the (Al) + Al 11 La 3 mixture, and its temperature is very close to the eutectic in the Al–La binary phase diagram (628°C [ 34 ]). Although the (Al) + Al 11 La 3 mixture is also present in sample A, it could not be detected in the DSC analysis due to its low amount. Additional results (supplementary) are provided to confirm the presence of this phase in the microstructure. Conversely, the samples with increased La content (F–J) all exhibited very similar DSC cooling curves, each with three peaks (Fig. 1 b and supplementary), except for samples F and G. The first peak represents the solidification of Al 45 Cr 7 , the second corresponds to the solidification of the LaCr 2 Al 20 phase, and the third to a mixture of Al 11 La 3 and (Al). In samples F and G, one peak is not visible; as with sample A, it could not be detected in the DSC analysis due to its small amount, but the ternary LaCr 2 Al 20 phase was present and observable in the microstructure. Therefore, additional results (supplementary) are provided to confirm the presence of this phase in the microstructure. Table 2 also presents the enthalpies of solidification, which are negative because solidification is an exothermic reaction (Fig. 1 displays positive values due to the construction of the device). When examining the temperatures and enthalpies, no clear trend is observed for samples A–E, as the differences are minimal. However, a trend is evident for samples H–J. The enthalpy of the first peak increases, which correlates with the amount of LaCr 2 Al 20 ternary phase in the samples. This indicates that the amount of ternary phase in the microstructure increases from sample H to J (the microstructures are shown in the supplementary material). Table 2 Transformation temperatures and solidification enthalpies, determined from the DSC curves during cooling Sample Temperature/°C Enthalpy/J g − 1 T 1 T 2 T 3 Enthalpies of solidification, 1st peak Enthalpies of solidification, 2nd peak A 747.3 655.5 / -11.8 -307.2 B 746.3 647.9 628.5 -12.2 -267.5 C 750.8 646.4 631.0 -11.5 -269.6 D 745.2 644.4 626.3 -10.5 -239.5 E 744.4 655.3 634.4 -11.5 -269.8 F / 642.2 627.9 / -326.6 G / 652.1 630.5 / -305.6 H 718.5 648.7 627.6 -1.5 -293.9 I 708.8 649.1 630.6 -3.2 -247.8 J 718.4 649.4 630.5 -6.4 -260.6 Microstructure characterization The microstructural analysis confirmed the phase composition, and the results of the SEM analysis are summarised in Table 3 . Samples A–E (with increased Cr content) have a microstructure consisting of the binary phase Al 45 Cr 7 , the ternary phase Al 20 Cr 2 La, a mixture of (Al) + Al 11 La 3 , and an (Al) matrix. In contrast, samples F–J (with increased La content) consist of the ternary phase Al 20 Cr 2 La, a mixture of (Al) + Al 11 La 3 , and an (Al) matrix. Table 3 Phases in the microstructure after DSC analysis Sample Phases A Al 45 Cr 7 Al 20 Cr 2 La (Al) + Al 11 La 3 (Al) B Al 45 Cr 7 Al 20 Cr 2 La (Al) + Al 11 La 3 (Al) C Al 45 Cr 7 Al 20 Cr 2 La (Al) + Al 11 La 3 (Al) D Al 45 Cr 7 Al 20 Cr 2 La (Al) + Al 11 La 3 (Al) E Al 45 Cr 7 Al 20 Cr 2 La (Al) + Al 11 La 3 (Al) F (Al) + Al 11 La 3 Al 20 Cr 2 La / (Al) G (Al) + Al 11 La 3 Al 20 Cr 2 La / (Al) H (Al) + Al 11 La 3 Al 20 Cr 2 La / (Al) I (Al) + Al 11 La 3 Al 20 Cr 2 La / (Al) J (Al) + Al 11 La 3 Al 20 Cr 2 La / (Al) For illustration and better understanding, we have selected a sample with increased Cr content (Fig. 2 ) and another with increased La content (Fig. 3 ) to show their microstructures. Figure 2 shows the microstructure of sample C at two magnifications: (a at 800x and b) at 1500x). It is clear that the microstructure comprises the binary Al 45 Cr 7 phase (dark grey particles), the ternary Al 20 Cr 2 La phase (lighter grey particles), a mixture of (Al) + Al 11 La 3 (white particles), and an (Al) matrix. Notably, the ternary Al 20 Cr 2 La phases can be observed around the binary Al 45 Cr 7 phases. This is visible in both figures but is clearer at higher magnification (Fig. 2 b). Figure 3 shows the microstructure of sample I at two magnifications (a at 500x and b) at 700x). Here, the microstructure consists of the ternary Al 20 Cr 2 La phase (grey, sharp-edged particles), a mixture of (Al) + Al 11 La 3 (white particles surrounding the grains), and an (Al) matrix. In this case, it is evident that the ternary phase is not present around a binary phase, unlike the samples with increased Cr content (A–E). An EDS analysis was performed on all investigated samples to confirm the previously mentioned phase stoichiometry. The results are presented for sample C (Fig. 4 ) and sample H (Fig. 5 ). For sample C (Fig. 4 ), the microstructure clearly consists of a mixture of (Al) + Al 11 La 3 (Fig. 4 a – spectra 1 and 2), a ternary Al 20 Cr 2 La phase (Fig. 4 b – spectrum 1), a binary Al 45 Cr 7 phase (Fig. 4 b – spectrum 2), and an (Al) matrix (Fig. 4 a – spectrum 3). In contrast, the microstructure of samples with increased La content (e.g. sample H, Fig. 5 ) consists of a ternary Al 20 Cr 2 La phase (Fig. 5 a – spectra 1 and 2), a mixture of (Al) + Al 11 La 3 (Fig. 5 b – spectrum 1), and an (Al) matrix (Fig. 5 a – spectrum 3). There is also a notable difference in the composition of the matrix: the matrix of the La-rich samples (F–J) contains only dissolved Cr and no detectable La, whereas the matrix of the Cr-rich samples (A–E) contains both dissolved Cr and La. Based on the results presented, the non-equilibrium solidification of alloys from the ternary phase system Al-Cr-La, for alloys with increased Cr content (A–E), proceeds as follows: $$\:\begin{array}{c}L\leftrightarrow\:L+\:{Al}_{45}{Cr}_{7}\:\leftrightarrow\:L+\:{Al}_{45}{Cr}_{7}+{Al}_{20}{Cr}_{2}La+\left(Al\right)\leftrightarrow\:{Al}_{45}{Cr}_{7}+{Al}_{20}{Cr}_{2}La+\left(\text{A}\text{l}\right)+{Al}_{11}{La}_{3}\:\#\left(1\right)\end{array}$$ Since we have found a mixture of Al 11 La 3 + (Al), there is no other way to explain the solidification as described in the observed sequence (1). To demonstrate that the mentioned eutectic phase forms last, an additional image is provided in the supplementary material, where droplets of the eutectic phase are visible. For samples with increased La content (F–J), however, the solidification path can be described as follows: $$\:\begin{array}{c}L\leftrightarrow\:L+\:{Al}_{45}{Cr}_{7}\:\leftrightarrow\:L+{Al}_{20}{Cr}_{2}La+{Al}_{45}{Cr}_{7}\:\leftrightarrow\:{Al}_{20}{Cr}_{2}La+\left(\text{A}\text{l}\right)+{Al}_{11}{La}_{3}\:\#\left(2\right)\end{array}$$ This means that the binary Al 45 Cr 7 phase transforms completely into the ternary Al 20 Cr 2 La phase. The binary phase is present in the microstructure of samples A–E, but is absent in samples F–J. CONCLUSIONS The results of this study support the following conclusions: Even a very small amount of alloying elements (Cr and/or La) can produce a wide range of microstructures, as shown by the microstructural characterisation. The microstructure of the samples with increased Cr content (A–E) consists of the binary Al 45 Cr 7 phase, the ternary Al 20 Cr 2 La phase, a mixture of (Al) + Al 11 La 3 , and an (Al) matrix. The ternary Al 20 Cr 2 La phases are observed around the binary Al 45 Cr 7 phases. The microstructure of the samples with increased La content (F–J) consists of the ternary Al 20 Cr 2 La phase, a mixture of (Al) + Al 11 La 3 , and an (Al) matrix. No significant trend was observed in the transformation temperatures as a function of chemical composition. In samples H–J, the proportion of the ternary Al 20 Cr 2 La phase increases, which is also reflected in the increase in the solidification enthalpy of the first peak. However, this was not observed in samples A–E. The solidification behaviour differs slightly in alloys with increased Cr content, as those with higher Cr content first form a binary Al 45 Cr 7 phase, followed by a ternary Al 20 Cr 2 La phase, then (Al), and finally a mixture of (Al) + Al 11 La 3 . In the solid state, the microstructure contains four phases: the binary Al 45 Cr 7 phase, the ternary Al 20 Cr 2 La phase, the (Al) + Al 11 La 3 mixture, and the (Al) matrix. The binary Al 45 Cr 7 phase is absent from the microstructure of samples with higher La content, so the solidification path differs only slightly. In these cases, solidification also begins with the binary Al 45 Cr 7 phase, followed by the ternary Al 20 Cr 2 La phase and (Al), and finally the (Al) + Al 11 La 3 mixture. In the solid state, three phases are present in the microstructure: the ternary Al 20 Cr 2 La phase, the (Al) + Al 11 La 3 mixture, and the (Al) matrix. Based on these findings, we expect that the ternary Al 20 Cr 2 La phase positively influences the microstructure, similar to the binary Al 45 Cr 7 phase. As even a small amount of La promotes the formation of this ternary phase, it could provide significant economic benefits for the development of new aluminium alloys. Declarations Conflict of interest The authors declare that they have no conflicts of interest. Author Contribution All authors contributed to the conception and design of the study. Preparation of materials, conducting the experiments, data collection and analysis were carried out by Tilen Balaško, Jožef Medved and Simona Delsante. The first draft of the manuscript was written by Tilen Balaško and all authors commented on earlier versions of the manuscript. All authors read and approved the final manuscript. Acknowledgement We gratefully acknowledge the support of the work by the Slovenian Research And Innovation Agency (ARIS) program P1-0195 (B). References Hosseinifar M, Malakhov D V. Effect of Ce and la on microstructure and properties of a 6xxx series type aluminum alloy. J Mater Sci. 2008;43:7157–64. https://doi.org/10.1007/s10853-008-3022-2 Yuan WH, An BL. Effect of la addition on the microstructures and mechanical properties of 7075 aluminum alloy. Adv Mater Res. 2011;152–153:1810–3. https://doi.org/10.4028/www.scientific.net/AMR.152-153.1810 Xu Y, Peng Z, Ding D, Zhang W, Gao Y, Chen G, et al. 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06:36:52","extension":"html","order_by":30,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":106123,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7796354/v1/1d0cdc7c71210a8c25816720.html"},{"id":95172035,"identity":"635fa14d-174a-4bc8-8477-2a8f84ea11d7","added_by":"auto","created_at":"2025-11-05 06:36:52","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":461158,"visible":true,"origin":"","legend":"\u003cp\u003eDSC cooling curves for sample C (a) and sample I (b)\u003c/p\u003e","description":"","filename":"Fig1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7796354/v1/19a65f74fabf44a8fab07f5e.jpg"},{"id":95228022,"identity":"a3b2cb72-2ea6-4dc7-98f6-20ee0903d4f2","added_by":"auto","created_at":"2025-11-05 16:33:18","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":622059,"visible":true,"origin":"","legend":"\u003cp\u003eMicrostructure of sample C, at 800x (a) and 1500x (b) magnification, with labelled corresponding phases\u003c/p\u003e","description":"","filename":"Fig2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7796354/v1/32660aeefc1787cb184c0ff4.jpg"},{"id":95172025,"identity":"a0b3782f-48db-455e-aba4-05696c79df72","added_by":"auto","created_at":"2025-11-05 06:36:52","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":657425,"visible":true,"origin":"","legend":"\u003cp\u003eMicrostructure of sample I, at 500x (a) and 700x (b) magnification, with labelled corresponding phases\u003c/p\u003e","description":"","filename":"Fig3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7796354/v1/6cb9649cfa4d95d2f51415c6.jpg"},{"id":95226620,"identity":"007f9625-cd31-4b14-ad80-ae7a617de299","added_by":"auto","created_at":"2025-11-05 16:31:28","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":347802,"visible":true,"origin":"","legend":"\u003cp\u003eThe areas analysed with EDS (marked as a spectrum in the tables below the microstructure) are indicated with the corresponding chemical composition in at% for sample C\u003c/p\u003e","description":"","filename":"Fig4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7796354/v1/364a3e2978b30849744aa1b5.jpg"},{"id":95226717,"identity":"650f3137-55bd-40bc-85eb-4668f1bb0748","added_by":"auto","created_at":"2025-11-05 16:31:40","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":343680,"visible":true,"origin":"","legend":"\u003cp\u003eThe areas analysed with EDS (indicated as a spectrum in the tables below the microstructure) are shown with the corresponding chemical composition in at% for sample H\u003c/p\u003e","description":"","filename":"Fig5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7796354/v1/4d6d494bdb5409738a602e5a.jpg"},{"id":95230679,"identity":"ede8acf9-1f34-448f-97e1-d0759d534937","added_by":"auto","created_at":"2025-11-05 16:38:16","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3121872,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7796354/v1/500a16db-f0bd-498d-8f6b-40bf4aeb2d11.pdf"},{"id":95172038,"identity":"176ae0e4-5b93-4c1f-a7c3-58464ab13b78","added_by":"auto","created_at":"2025-11-05 06:36:52","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":2886224,"visible":true,"origin":"","legend":"","description":"","filename":"Supplementarymaterial.docx","url":"https://assets-eu.researchsquare.com/files/rs-7796354/v1/9c40588ece6cc799169c261b.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"A Study on the Solidification Behaviour of Al-Cr-La Alloys in the Aluminium-Rich Region","fulltext":[{"header":"INTRODUCTION","content":"\u003cp\u003eThe ternary Al-Cr-La system still contains many unknowns. This system has attracted attention because aluminium alloys are now frequently alloyed with rare earth elements (REE) to achieve improved mechanical and physical properties. Other researchers [\u003cspan additionalcitationids=\"CR2 CR3 CR4 CR5 CR6 CR7 CR8\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] have shown that the addition of La enhances the mechanical and corrosion properties, partly due to the refinement of (Al) crystal grains and a reduction in secondary dendrite arm spacing (SDAS) [\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Studies indicate that the addition of La in binary and ternary systems not only refines (Al) grains but also promotes the precipitation of Mg\u003csub\u003e2\u003c/sub\u003eSi [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] and modifies the Al\u003csub\u003e13\u003c/sub\u003eFe\u003csub\u003e4\u003c/sub\u003e [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e], Mg\u003csub\u003e2\u003c/sub\u003eSi [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] and β-AlFeSi [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] phases. Furthermore, in high-strength 7xxx-series aluminium alloys with added Cr, La additions have been found to modify the Al\u003csub\u003e45\u003c/sub\u003eCr\u003csub\u003e7\u003c/sub\u003e phase and form the ternary Al\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa phase [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Given these positive effects of La additions to aluminium alloys, this influences the growth potential of demand for such alloys, as previously mentioned [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eConsidering that 7xxx series aluminium alloys are widely used in transportation [\u003cspan additionalcitationids=\"CR16 CR17 CR18 CR19 CR20 CR21\" citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], their improved mechanical properties through La additions offer several advantages. Firstly, these improved properties could broaden their applications in the transport industry and potentially enable them to replace steel in certain structural components. Secondly, aluminium alloys possess an excellent strength-to-mass ratio due to their lower density compared to steels. Consequently, higher mechanical properties can result in reduced mass in cars, lorries, trains, and aeroplanes. Reduced mass directly leads to lower fuel consumption and a smaller carbon footprint [\u003cspan additionalcitationids=\"CR24\" citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. For example, car manufacturers have already committed to reducing average carbon emissions by 37.5% between 2021 and 2030 [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. As a result, the average Al content in passenger cars is projected to increase from 121 kg in 2006 to 256 kg in 2030 (net mass) [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e], with the overall use of aluminium alloys in transport expected to rise by 55% from 2017 to 2030 [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eIn order to better understand the effects of La addition to Cr-containing alloys, this study examines the solidification behaviour and phase evolution of alloys in the Al-Cr-La ternary system, particularly in the aluminium-rich corner. Differential scanning calorimetry (DSC) was used to evaluate transformation temperatures and clarify the solidification path. Microstructural analyses were performed using scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDXS) analysis to investigate phase evolution.\u003c/p\u003e"},{"header":"EXPERIMENTAL WORK","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eMaterials\u003c/h2\u003e\u003cp\u003eThe alloys were produced in a vacuum arc melting system (MTI SP-MSM208) using a non-consumable tungsten electrode and a water-cooled copper furnace. Pure Al (99.99 mass%), Cr (99.99 mass%) and La (99.99 mass%) were used as starting materials. A high-purity Ar atmosphere (Ar 6.0, 99.9999%) was maintained and further purified by melting a Ti getter (99.7 mass%). Before introducing the Ar, the melting chamber was evacuated, and the residual pressure was monitored with a vacuum gauge. To ensure chemical homogeneity, the alloys were remelted four times. After production, homogenisation was carried out in a Xiamen Tmax Battery Equipments Limited SK2-4-12TPB3 tube furnace under an inert Ar (Ar 5.0, 99.999%) atmosphere. To further purify the inert gas and prevent oxidation, Mg crisps (99.99 mass%) were added to the tube as an oxygen carrier. The samples were stored in Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e crucibles prior to homogenisation, which was performed at 600\u0026deg;C for 600 hours. After homogenisation, the samples were quenched in ice-cold water to obtain the equilibrium structure. The chemical composition (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) was measured with the OES ARL iSpark 8860.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eChemical composition of the investigated alloys in at%\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eSample\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e\u003cp\u003eat%\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAl\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eCr\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eLa\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eA\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e98.67\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.03\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eB\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e98.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eC\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e98.70\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.10\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eD\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e99.07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.76\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.17\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eE\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e99.09\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.83\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.08\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eF\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e99.57\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.40\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eG\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e99.50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.30\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eH\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e99.30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.40\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eI\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e98.80\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.70\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.50\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eJ\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e97.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.00\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eDifferential scanning calorimetry (DSC)\u003c/h3\u003e\n\u003cp\u003eSamples measuring approximately 3.5 x 3.5 x 2.0 mm (\u0026plusmn;\u0026thinsp;0.2 mm) and with a mass between 30 and 50 mg were prepared from the alloys for differential scanning calorimetry (DSC) analysis. The solidification path was examined using a NETZSCH STA 449 C Jupiter instrument. The samples were heated to 1100\u0026deg;C at 10 K min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and cooled to room temperature at the same rate, with the furnace maintained under a protective argon atmosphere during the analysis. Empty Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e crucibles served as the reference. Only the cooling curves were used for analysis, as the study focused on solidification. The DSC analysis determined the transformation temperatures of the solidification path, with phase transformation temperatures evaluated according to the recommendations of Boettinger et al. [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. DSC analysis provides highly accurate results for studying the solidification process of metals and alloys, as repeatedly reported in previous studies [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e].\u003c/p\u003e\n\u003ch3\u003eMetallographic analyses\u003c/h3\u003e\n\u003cp\u003eBefore metallographic analysis, the samples were ground with silicon carbide paper and polished with a diamond\u0026ndash;water suspension on fabric discs. Optical microscopy was performed using a Leica DM4000 M optical microscope equipped with an AxioCam ERc 5s high-resolution digital camera. The microstructure was then analysed with a Zeiss EVO 40 SEM equipped with a PentaFET EDXS detector (Oxford Instruments) using the backscattered electron (BSE) imaging mode.\u003c/p\u003e"},{"header":"RESULTS AND DISCUSSION","content":"\u003cp\u003eThe results of the DSC analysis are shown for the temperature range between 550\u0026deg;C and 850\u0026deg;C, during which the solidification process was analysed. The figures in this section were selected based on the different sample compositions, and only the most representative results are presented.\u003c/p\u003e\n\u003ch3\u003eDSC analysis\u003c/h3\u003e\n\u003cp\u003eThe DSC analysis of the samples with increased Cr content (A\u0026ndash;E) revealed two peaks for sample A (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea) and 3 peaks for samples B\u0026ndash;E (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and supplementary), although for these samples the third peak appears only as a \u0026ldquo;shoulder\u0026rdquo; on the low-temperature big peak. It was expected that the Al\u003csub\u003e45\u003c/sub\u003eCr\u003csub\u003e7\u003c/sub\u003e binary phase (also known as Al\u003csub\u003e7\u003c/sub\u003eCr and Al\u003csub\u003e13\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003e) [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e] would begin to solidify first, as the Al\u0026ndash;Cr binary phase diagram shows a higher melting point, indicating that this phase is typically present in molten Al at these temperatures. Indeed, this property is used industrially to refine the cast grain structure and prevent excessive growth of (Al) crystal grains during heat treatment [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. Thus, while the first peak in samples A\u0026ndash;E indicates the solidification of Al\u003csub\u003e45\u003c/sub\u003eCr\u003csub\u003e7\u003c/sub\u003e, the second peak corresponds to the solidification of the LaCr\u003csub\u003e2\u003c/sub\u003eAl\u003csub\u003e20\u003c/sub\u003e phase and a mixture of Al\u003csub\u003e45\u003c/sub\u003eCr\u003csub\u003e7\u003c/sub\u003e + (Al). The third, unexpected peak was confirmed by subsequent microstructure analysis (the microstructure of all mentioned samples also consists of a mixture of (Al)\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e), indicating that the third peak (\u0026ldquo;shoulder\u0026rdquo;) corresponds to the solidification of the (Al)\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e mixture, and its temperature is very close to the eutectic in the Al\u0026ndash;La binary phase diagram (628\u0026deg;C [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]). Although the (Al)\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e mixture is also present in sample A, it could not be detected in the DSC analysis due to its low amount. Additional results (supplementary) are provided to confirm the presence of this phase in the microstructure.\u003c/p\u003e\u003cp\u003eConversely, the samples with increased La content (F\u0026ndash;J) all exhibited very similar DSC cooling curves, each with three peaks (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb and supplementary), except for samples F and G. The first peak represents the solidification of Al\u003csub\u003e45\u003c/sub\u003eCr\u003csub\u003e7\u003c/sub\u003e, the second corresponds to the solidification of the LaCr\u003csub\u003e2\u003c/sub\u003eAl\u003csub\u003e20\u003c/sub\u003e phase, and the third to a mixture of Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e and (Al). In samples F and G, one peak is not visible; as with sample A, it could not be detected in the DSC analysis due to its small amount, but the ternary LaCr\u003csub\u003e2\u003c/sub\u003eAl\u003csub\u003e20\u003c/sub\u003e phase was present and observable in the microstructure. Therefore, additional results (supplementary) are provided to confirm the presence of this phase in the microstructure.\u003c/p\u003e\u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e also presents the enthalpies of solidification, which are negative because solidification is an exothermic reaction (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e displays positive values due to the construction of the device).\u003c/p\u003e\u003cp\u003eWhen examining the temperatures and enthalpies, no clear trend is observed for samples A\u0026ndash;E, as the differences are minimal. However, a trend is evident for samples H\u0026ndash;J. The enthalpy of the first peak increases, which correlates with the amount of LaCr\u003csub\u003e2\u003c/sub\u003eAl\u003csub\u003e20\u003c/sub\u003e ternary phase in the samples. This indicates that the amount of ternary phase in the microstructure increases from sample H to J (the microstructures are shown in the supplementary material).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eTransformation temperatures and solidification enthalpies, determined from the DSC curves during cooling\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eSample\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e\u003cp\u003eTemperature/\u0026deg;C\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u003cp\u003eEnthalpy/J g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eT\u003csub\u003e1\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eT\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eT\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eEnthalpies of solidification,\u003c/p\u003e\u003cp\u003e1st peak\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eEnthalpies of solidification,\u003c/p\u003e\u003cp\u003e2nd peak\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eA\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e747.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e655.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e/\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-11.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e-307.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eB\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e746.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e647.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e628.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-12.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e-267.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eC\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e750.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e646.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e631.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-11.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e-269.6\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eD\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e745.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e644.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e626.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-10.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e-239.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eE\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e744.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e655.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e634.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-11.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e-269.8\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eF\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e/\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e642.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e627.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e/\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e-326.6\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eG\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e/\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e652.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e630.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e/\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e-305.6\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eH\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e718.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e648.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e627.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-1.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e-293.9\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eI\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e708.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e649.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e630.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-3.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e-247.8\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eJ\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e718.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e649.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e630.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-6.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e-260.6\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003eMicrostructure characterization\u003c/h2\u003e\u003cp\u003eThe microstructural analysis confirmed the phase composition, and the results of the SEM analysis are summarised in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. Samples A\u0026ndash;E (with increased Cr content) have a microstructure consisting of the binary phase Al\u003csub\u003e45\u003c/sub\u003eCr\u003csub\u003e7\u003c/sub\u003e, the ternary phase Al\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa, a mixture of (Al)\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e, and an (Al) matrix. In contrast, samples F\u0026ndash;J (with increased La content) consist of the ternary phase Al\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa, a mixture of (Al)\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e, and an (Al) matrix.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003ePhases in the microstructure after DSC analysis\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSample\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"4\" nameend=\"c5\" namest=\"c2\"\u003e\u003cp\u003ePhases\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eA\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAl\u003csub\u003e45\u003c/sub\u003eCr\u003csub\u003e7\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAl\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e(Al)\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e(Al)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eB\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAl\u003csub\u003e45\u003c/sub\u003eCr\u003csub\u003e7\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAl\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e(Al)\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e(Al)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eC\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAl\u003csub\u003e45\u003c/sub\u003eCr\u003csub\u003e7\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAl\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e(Al)\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e(Al)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eD\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAl\u003csub\u003e45\u003c/sub\u003eCr\u003csub\u003e7\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAl\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e(Al)\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e(Al)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eE\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAl\u003csub\u003e45\u003c/sub\u003eCr\u003csub\u003e7\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAl\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e(Al)\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e(Al)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eF\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(Al)\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAl\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e/\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e(Al)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eG\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(Al)\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAl\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e/\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e(Al)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eH\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(Al)\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAl\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e/\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e(Al)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eI\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(Al)\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAl\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e/\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e(Al)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eJ\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(Al)\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAl\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e/\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e(Al)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eFor illustration and better understanding, we have selected a sample with increased Cr content (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) and another with increased La content (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) to show their microstructures. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows the microstructure of sample C at two magnifications: (a at 800x and b) at 1500x). It is clear that the microstructure comprises the binary Al\u003csub\u003e45\u003c/sub\u003eCr\u003csub\u003e7\u003c/sub\u003e phase (dark grey particles), the ternary Al\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa phase (lighter grey particles), a mixture of (Al)\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e (white particles), and an (Al) matrix. Notably, the ternary Al\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa phases can be observed around the binary Al\u003csub\u003e45\u003c/sub\u003eCr\u003csub\u003e7\u003c/sub\u003e phases. This is visible in both figures but is clearer at higher magnification (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e shows the microstructure of sample I at two magnifications (a at 500x and b) at 700x). Here, the microstructure consists of the ternary Al\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa phase (grey, sharp-edged particles), a mixture of (Al)\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e (white particles surrounding the grains), and an (Al) matrix. In this case, it is evident that the ternary phase is not present around a binary phase, unlike the samples with increased Cr content (A\u0026ndash;E).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAn EDS analysis was performed on all investigated samples to confirm the previously mentioned phase stoichiometry. The results are presented for sample C (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) and sample H (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). For sample C (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e), the microstructure clearly consists of a mixture of (Al)\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea \u0026ndash; spectra 1 and 2), a ternary Al\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa phase (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb \u0026ndash; spectrum 1), a binary Al\u003csub\u003e45\u003c/sub\u003eCr\u003csub\u003e7\u003c/sub\u003e phase (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb \u0026ndash; spectrum 2), and an (Al) matrix (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea \u0026ndash; spectrum 3). In contrast, the microstructure of samples with increased La content (e.g. sample H, Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e) consists of a ternary Al\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa phase (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea \u0026ndash; spectra 1 and 2), a mixture of (Al)\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb \u0026ndash; spectrum 1), and an (Al) matrix (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea \u0026ndash; spectrum 3). There is also a notable difference in the composition of the matrix: the matrix of the La-rich samples (F\u0026ndash;J) contains only dissolved Cr and no detectable La, whereas the matrix of the Cr-rich samples (A\u0026ndash;E) contains both dissolved Cr and La.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eBased on the results presented, the non-equilibrium solidification of alloys from the ternary phase system Al-Cr-La, for alloys with increased Cr content (A\u0026ndash;E), proceeds as follows:\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:\\begin{array}{c}L\\leftrightarrow\\:L+\\:{Al}_{45}{Cr}_{7}\\:\\leftrightarrow\\:L+\\:{Al}_{45}{Cr}_{7}+{Al}_{20}{Cr}_{2}La+\\left(Al\\right)\\leftrightarrow\\:{Al}_{45}{Cr}_{7}+{Al}_{20}{Cr}_{2}La+\\left(\\text{A}\\text{l}\\right)+{Al}_{11}{La}_{3}\\:\\#\\left(1\\right)\\end{array}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eSince we have found a mixture of Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e + (Al), there is no other way to explain the solidification as described in the observed sequence (1). To demonstrate that the mentioned eutectic phase forms last, an additional image is provided in the supplementary material, where droplets of the eutectic phase are visible.\u003c/p\u003e\u003cp\u003eFor samples with increased La content (F\u0026ndash;J), however, the solidification path can be described as follows:\u003cdiv id=\"Equb\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e\n$$\\:\\begin{array}{c}L\\leftrightarrow\\:L+\\:{Al}_{45}{Cr}_{7}\\:\\leftrightarrow\\:L+{Al}_{20}{Cr}_{2}La+{Al}_{45}{Cr}_{7}\\:\\leftrightarrow\\:{Al}_{20}{Cr}_{2}La+\\left(\\text{A}\\text{l}\\right)+{Al}_{11}{La}_{3}\\:\\#\\left(2\\right)\\end{array}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThis means that the binary Al\u003csub\u003e45\u003c/sub\u003eCr\u003csub\u003e7\u003c/sub\u003e phase transforms completely into the ternary Al\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa phase. The binary phase is present in the microstructure of samples A\u0026ndash;E, but is absent in samples F\u0026ndash;J.\u003c/p\u003e\u003c/div\u003e"},{"header":"CONCLUSIONS","content":"\u003cp\u003eThe results of this study support the following conclusions:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eEven a very small amount of alloying elements (Cr and/or La) can produce a wide range of microstructures, as shown by the microstructural characterisation.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eThe microstructure of the samples with increased Cr content (A\u0026ndash;E) consists of the binary Al\u003csub\u003e45\u003c/sub\u003eCr\u003csub\u003e7\u003c/sub\u003e phase, the ternary Al\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa phase, a mixture of (Al)\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e, and an (Al) matrix. The ternary Al\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa phases are observed around the binary Al\u003csub\u003e45\u003c/sub\u003eCr\u003csub\u003e7\u003c/sub\u003e phases.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eThe microstructure of the samples with increased La content (F\u0026ndash;J) consists of the ternary Al\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa phase, a mixture of (Al)\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e, and an (Al) matrix.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eNo significant trend was observed in the transformation temperatures as a function of chemical composition. In samples H\u0026ndash;J, the proportion of the ternary Al\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa phase increases, which is also reflected in the increase in the solidification enthalpy of the first peak. However, this was not observed in samples A\u0026ndash;E.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eThe solidification behaviour differs slightly in alloys with increased Cr content, as those with higher Cr content first form a binary Al\u003csub\u003e45\u003c/sub\u003eCr\u003csub\u003e7\u003c/sub\u003e phase, followed by a ternary Al\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa phase, then (Al), and finally a mixture of (Al)\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e. In the solid state, the microstructure contains four phases: the binary Al\u003csub\u003e45\u003c/sub\u003eCr\u003csub\u003e7\u003c/sub\u003e phase, the ternary Al\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa phase, the (Al)\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e mixture, and the (Al) matrix.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eThe binary Al\u003csub\u003e45\u003c/sub\u003eCr\u003csub\u003e7\u003c/sub\u003e phase is absent from the microstructure of samples with higher La content, so the solidification path differs only slightly. In these cases, solidification also begins with the binary Al\u003csub\u003e45\u003c/sub\u003eCr\u003csub\u003e7\u003c/sub\u003e phase, followed by the ternary Al\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa phase and (Al), and finally the (Al)\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e mixture. In the solid state, three phases are present in the microstructure: the ternary Al\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa phase, the (Al)\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e mixture, and the (Al) matrix.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eBased on these findings, we expect that the ternary Al\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa phase positively influences the microstructure, similar to the binary Al\u003csub\u003e45\u003c/sub\u003eCr\u003csub\u003e7\u003c/sub\u003e phase. As even a small amount of La promotes the formation of this ternary phase, it could provide significant economic benefits for the development of new aluminium alloys.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eConflict of interest\u003c/h2\u003e\u003cp\u003eThe authors declare that they have no conflicts of interest.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eAll authors contributed to the conception and design of the study. Preparation of materials, conducting the experiments, data collection and analysis were carried out by Tilen Balaško, Jožef Medved and Simona Delsante. The first draft of the manuscript was written by Tilen Balaško and all authors commented on earlier versions of the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eWe gratefully acknowledge the support of the work by the Slovenian Research And Innovation Agency (ARIS) program P1-0195 (B).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eHosseinifar M, Malakhov D V. Effect of Ce and la on microstructure and properties of a 6xxx series type aluminum alloy. J Mater Sci. 2008;43:7157\u0026ndash;64. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s10853-008-3022-2\u003c/span\u003e\u003cspan address=\"10.1007/s10853-008-3022-2\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eYuan WH, An BL. Effect of la addition on the microstructures and mechanical properties of 7075 aluminum alloy. 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J Phase Equilibria Diffus. 2007;28:581\u0026ndash;581. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s11669-007-9178-7\u003c/span\u003e\u003cspan address=\"10.1007/s11669-007-9178-7\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Al-Cr-La, solidification, DSC, microstructure","lastPublishedDoi":"10.21203/rs.3.rs-7796354/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7796354/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study examines the solidification behaviour of Al-Cr-La alloys, reflecting the increasing use of rare-earth elements to enhance the properties of aluminium alloys. The research aims to determine how the new ternary phase Al\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa, formed by the addition of La, influences the solidification process. This fundamental understanding is essential before these alloys can be developed for high-performance applications. Ten alloys with varying Cr and La contents were produced using an arc melter. After annealing, their solidification and microstructure were analysed using DSC and SEM. In alloys with higher Cr content, solidification begins with the Al\u003csub\u003e45\u003c/sub\u003eCr\u003csub\u003e7\u003c/sub\u003e phase, followed by the ternary Al\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa phase, then (Al), and finally a mixture of (Al)\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e. Thus, these samples (A\u0026ndash;E) exhibit four phases: Al\u003csub\u003e45\u003c/sub\u003eCr\u003csub\u003e7\u003c/sub\u003e, Al\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa, (Al), and Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e. (Al) is present in the matrix and mixed with Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e, while the ternary Al\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa phase is observed around the binary Al\u003csub\u003e45\u003c/sub\u003eCr\u003csub\u003e7\u003c/sub\u003e phase. In samples F\u0026ndash;J, solidification also begins with the binary Al\u003csub\u003e45\u003c/sub\u003eCr\u003csub\u003e7\u003c/sub\u003e phase, followed by the ternary Al\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa phase and (Al), and finally the (Al)\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e mixture. In this case, the microstructure of samples with increased La content (F\u0026ndash;J) consists of the ternary Al\u003csub\u003e20\u003c/sub\u003eCr\u003csub\u003e2\u003c/sub\u003eLa phase, the (Al)\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e11\u003c/sub\u003eLa\u003csub\u003e3\u003c/sub\u003e mixture, and an (Al) matrix.\u003c/p\u003e","manuscriptTitle":"A Study on the Solidification Behaviour of Al-Cr-La Alloys in the Aluminium-Rich Region","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-05 06:36:47","doi":"10.21203/rs.3.rs-7796354/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"5c7db299-c0d3-4257-b3a1-076b931d61de","owner":[],"postedDate":"November 5th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-11-05T06:36:47+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-05 06:36:47","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7796354","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7796354","identity":"rs-7796354","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}