Fatigue Property of Additively Manufactured Ti-6Al-4V under Non-proportional Multiaxial Loading

Abstract Low cycle fatigue strength properties of additively manufactured Ti-6Al-4V alloy were experimentally investigated under proportional and non-proportional multiaxial loading. Fatigue tests have been conducted by means of hollow cylinder specimens with and without heat treatments, at room temperature in air. Fatigue tests with proportional loading represented by a push-pull strain path and non-proportional loading represented by a circle strain path were conducted, respectively. The fatigue lives of additively manufactured specimens were drastically reduced obviously by internal voids and defects in comparison with the specimens used in the previous study [1]. In addition, the defect size is measured, and the defect does not cause fatigue strength reduction above some size. The fracture surface was observed using SEM to investigate fracture mechanism of additively manufactured specimens under two types of strain path. Different fracture patterns are recognized for the two strain paths; however, both showed the retention of the crack propagation in spite of the presence of numerous defects. The crack propagation properties of the materials with numerous defects under non-proportional multiaxial loading were elucidated to increase the reliability of additive manufactured components.