ABSTRACT

A high-oxygen (∼0.5 wt-%) Ti–6Al–4V alloy with a nanoscale heterogeneous structure consisting of ultrathin-lamellar-structured and coarse-grained domains was fabricated by powder processing and thermomechanical consolidation. In investigating the effect of heat treatment on this alloy, it was found that changing such nanoscale heterogeneous structure into a regular α/β lamellar structure, which was commonly produced in conventional fabrication routes, caused not only a significant decrease of strength but also a clear drop in tensile ductility. Analysis revealed that the intrinsic plasticity of coarse-grained domains and deformation coordination across domain boundaries captured microcracks and increased strain hardening rate, leading to the enhanced ductility of heterogeneous structure. In contrast, the intergranular fracture mode and inadequate variation of crystallographic orientations of α lamellae were ductility-deterioration mechanisms for the regular lamellar structure.

摘要

一种高氧（〜0.5 wt％）的Ti-6Al-4V合金，具有纳米级异质结构，由超薄层状结构和粗晶粒域组成，是通过粉末加工和热机械固结制成的。在研究热处理对该合金的影响时，发现将这种纳米级异质结构改变为规则的α / β通常在常规制造路线中生产的层状结构不仅导致强度显着降低，而且拉伸延展性明显下降。分析表明，粗晶粒域的固有塑性和跨域边界的变形协调捕获了微裂纹并提高了应变硬化速率，从而提高了异质结构的延展性。相比之下，α片晶的晶间断裂模式和晶体学取向的不充分变化是规则层状结构的延展性-劣化机制。