Research on the microstructural organization and mechanical properties of 5356 aluminum alloy arc additive manufacturing under low heat input conditions

Abstract To address the issue of excessive heat input during arc additive manufacturing of aluminum alloys, which leads to difficulties in forming and reduced dimensional accuracy, this paper investigates the microstructure and mechanical properties of 5356 aluminum alloy under low heat input conditions (30A, 40A, 50A, and 60A). The forming dimensions of multilayer single-pass straight-walled specimens under varying low-current conditions were analyzed, along with comprehensive tests on their mechanical properties, including microstructure, microhardness, and tensile strength. The results indicate that specimens can be successfully formed under different low-current conditions. Notably, at 40A, the front and upper surfaces of the specimens exhibit a smooth and flat appearance, contributing to an aesthetically superior outcome. The microstructure of the straight-walled specimen is predominantly composed of an α(Al) matrix and skeletal β(Al3Mg2). As the current increases, the distribution density of β(Al3Mg2) decreases, accompanied by a reduction in number and an increase in size. With increasing current, the microhardness initially rises, followed by a subsequent decline. Additionally, the microhardness shows a gradual increase from the bottom to the top of the specimen. As current increases, both the tensile strength and elongation of horizontal and vertical specimens first increase and then decrease. It is observed that the tensile strength and elongation of horizontal specimens are slightly higher than those of vertical specimens. This study lays a theoretical foundation for the application of arc additive manufacturing technology in processing 5356 aluminum alloys.