Impurities block the alpha to omega martensitic transformation in titanium

TL;DR

This study investigates how various impurities such as oxygen, nitrogen, carbon, aluminum, vanadium, and titanium vacancies influence the alpha to omega martensitic transformation in titanium, revealing impurity-induced suppression mechanisms.

Contribution

It provides a microscopic understanding of impurity effects on the alpha to omega transformation in titanium using ab initio calculations and a newly identified transformation pathway.

Findings

Impurities like O, N, C suppress the transformation.

Substitutional Al and V also inhibit the phase change.

The microscopic model explains experimental suppression in specific alloys.

Abstract

The onset and kinetics of martensitic transformations are controlled by impurities trapped during the transformation. For the alpha to omega transformation in Ti, ab initio methods yield the changes in both the relative stability of and energy barrier between the phases. Using the recently discovered transformation pathway, we study interstitial O, N, C; substitutional Al and V; and Ti interstitials and vacancies. The resulting microscopic picture explains the observations, specifically the suppression of the transformation in A-70 and Ti-6Al-4V titanium alloys.