Improvement of proof-ultimate strength difference in laser additive manufactured Ti–6Al–2V–1.5Mo–0.5Zr–0.3Si alloy by tuning basket-weave structure

摘要

After annealed at 1000 ℃, a special basket-weave structure is obtained in laser additive manufactured Ti–6Al–2V–1.5Mo–0.5Zr–0.3Si alloy. The unit of the special basket-weave structure is α lamellas clusters, which consist of lamellar primary α (αp), crab-like structures at the edges of αp and lamellar secondary α (αs) on both sides of ap. As the units of basket-weave structures, the width of the clusters is much larger than that of α lamellas in as-deposited alloy. The formation temperature and process of the special basket-weave structure are studied, and the room temperature properties are tested and compared with the as-deposited alloy. The results show that the formation of the special basket-weave structure finishes within about 30 s and crab-like structures form earlier than lamellar αs. The yield strength of the alloy is decreased by about 75 MPa compared to that of the as-deposited alloy. Besides, the proof-ultimate strength difference of the alloy is two times higher than that of the as-deposited alloy with about 34％ improvement for the impact toughness. It is because α colony size shows a positive correlation to the width of the unit forming basket-weave structure. The enhancement in proof-ultimate strength difference could significantly improve the toughness of the alloy, and thus effectively increase the safety of the alloy.