Twinning–Detwinning Deformation Mechanism in Ti–15Mo Alloy and Its Effect on the Microstructure Evolution and Yield Strength

Abstract

{332}<113> twinning is an important deformation mode for metastable β–Ti alloys. However, little is known on the reverse detwinning process and its hardening effect. Herein, detwinning behavior in Ti–15Mo alloy and its effect on the microstructure evolution and yield strength is investigated. Twins are generated during pre‐tension along the rolling direction. Then, the pre‐twinned samples are compressed in the same direction by different strains. It is shown that compressive yield strength is significantly improved by pre‐tension compared with the as‐received alloy. Microstructure characterization reveals that almost all the twins generated in pre‐tension were detwinned during the reverse compression. New twins appear in some β grains by increasing the compression strain. The variant with the highest Schmid factor (SF) is likely selected for twinning. Some paired twins formed at grain boundaries do not have the highest SF, but have a large strain compatibility factor (m′), implying a strong influence from local stress. Profuse slip traces are observed, which transferred across the detwinned regions during the reverse compression, causing severe stress concentrations in the primary twin domains. Based on the experimental observations, a possible strengthening mechanism by the twinning–detwinning behavior is proposed and discussed.