Processing‐Induced Microstructural Heterogeneity Governing Cyclic Stress–Strain Behavior and Damage Mechanisms of Ti6Al4V Fabricated by Electron Beam Selective Melting and Casting

The cyclic stress–strain behavior and damage mechanisms of Ti6Al4V alloys fabricated by electron beam selective melting (EBSM) and conventional casting are systematically investigated under total strain amplitudes of Δ ε t /2 = ±0.32%, ±0.60%, and ±1.20%. The original EBSMTi6Al4V alloy exhibits a fine basketweave microstructure, whereas the CASTTi6Al4V alloy shows a coarse lamellar microstructure. Both alloys display cyclic stabilization at Δ ε t /2 = ±0.32% and cyclic softening at Δ ε t /2 = ±0.60% and ±1.20%. At strain amplitudes of ±0.60% and ±1.20%, the EBSMTi6Al4V alloy demonstrates significantly improved fatigue life. This enhancement is attributed to higher local misorientation, nanosized β phases, and α′/α interfaces, which effectively impede dislocation motion. Fatigue cracks initiate at the surface in both alloys, however, the EBSM alloy exhibits ductile fracture, while the cast alloy shows cleavage‐dominated fracture.