The Nucleation and the Intrinsic Microstructure Evolution of Martensite from 332113β Twin Boundary in β Titanium: First-Principles Calculations

Abstract

A clear understanding on the inter-evolution behaviors between 332113β twinning and stress-induced martensite (SIM) α″ in β-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 α″ from 332113β twin boundary (TB) were investigated in pure β-Ti at atomic scale using first-principles calculations in this work. We found the α″ precipitation prefers to nucleate and grow at 332113β TB, with the transformation of 332113β TB→130310α” TB. During this process, α″ precipitation firstly nucleates at 332113β TB and, subsequently, it grows inwards toward the grain interiors. This easy transition may stem from the strong crystallographic correspondence between 332113β and 130310α” TBs, and the region close to the 332113β TB presents the characteristics of intermediate structure between β and α″ phases. Kinetics calculations indicate the α″ phase barrierlessly nucleates at 332113β 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 α″ from 332113β TB, which may deepen our understanding on the precipitation of martensite α″ and the inter-evolution behaviors between 332113β twinning and martensite α″ in β-Ti alloys at atomic scale.