Origin of the ω-Strengthening and Embrittlement in β-Titanium Alloys: Insight from First Principles

Abstract

The ω-phase precipitates in β-Ti alloys increase the strength but significantly degrade the ductility of the alloys. In the present work, the mechanism of ω-strengthening and embrittlement is investigated by using a first principles method based on density functional theory. The generalized stacking fault energies of various slip systems in both the β and ω phases are calculated. The strengthening and embrittlement effects of the ω phase are discussed by comparing the slip energy barriers of slip systems in the β and ω phases with different orientation relationships. It is found that the slip energy barriers of slip systems in the ω phase, except for $$(\bar 2020){[0001]_\omega },$$ are much higher than those of slip systems in the β phase, which explains the ω-strengthening and embrittlement effects. The slip energy barrier of the most active slip system in the phase, $$(\bar 2020){[0001]_\omega },$$ increases with the depletion of Mo and increasing extent of structure collapse, suggesting that aging treatment enhances the -strengthening and embrittlement effects.