The Nucleation and the Intrinsic Microstructure Evolution of Martensite from {332}⟨113⟩β Twin Boundary in β Titanium: First-Principles Calculations

A clear understanding on the inter-evolution behaviors between {332}< 113 >(beta) twinning and stress-induced martensite (SIM) alpha '' in beta-Ti alloys is vital for improving its strength and ductility concurrently. As the preliminary step to better understand these complex behaviors, the nucleation and the intrinsic microstructure evolution of martensite alpha '' from {332}< 113 >(beta) twin boundary (TB) were investigated in pure beta-Ti at atomic scale using first-principles calculations in this work. We found the alpha '' precipitation prefers to nucleate and grow at {332}< 113 >(beta) TB, with the transformation of {332}< 113 >(beta) TB ->{130}<(3) over bar 10 >(alpha '') TB. During this process, alpha '' precipitation firstly nucleates at{332}< 113 >(beta) TB -> and, subsequently, it grows inwards toward the grain interiors. This easy transition may stem from the strong crystallographic correspondence between {332}< 113 >(beta) and {130}<(3) over bar 10 >(alpha '') TBs, and the region close to the f332 gh113 i fi TB presents the characteristics of intermediate structure between beta and alpha '' phases. Kinetics calculations indicate the alpha '' phase barrierlessly nucleates at{332}< 113 >(beta) TB rather than in grain interior, where there is higher critical driving energy. Our calculations provide a unique perspective on the intrinsic microstructure evolution of martensite alpha '' from {332}< 113 >(beta) TB, which may deepen our understanding on the precipitation of martensite alpha '' and the inter-evolution behaviors between {332}< 113 >(beta) twinning and martensite alpha '' in beta-Ti alloys at atomic scale.