Pressure-induced alpha-to-omega transition in titanium metal: A systematic study of the effects of uniaxial stress

TL;DR

This study systematically examines how uniaxial stress influences the pressure-induced alpha-to-omega phase transition in titanium, revealing that the transition pressure and phase coexistence depend on the pressure environment and stress conditions.

Contribution

It provides new insights into the effects of uniaxial stress and pressure environment on the alpha-to-omega transition in titanium, highlighting the importance of stress conditions.

Findings

Transition pressure varies with pressure medium from 4.9 GPa to 10.5 GPa.

Alpha and omega phases coexist over a broad pressure range.

Laser heating lowers the transition pressure.

Abstract

We investigated the effects of uniaxial stress on the pressure-induced alpha-to-omega transition in pure titanium (Ti) by means of angle dispersive x-ray diffraction in a diamond-anvil cell. Experiments under four different pressure environments reveal that: (1) the onset of the transition depends on the pressure medium used, going from 4.9 GPa (no pressure medium) to 10.5 GPa (argon pressure medium); (2) the a and w phases coexist over a rather large pressure range, which depends on the pressure medium employed; (3) the hysteresis and quenchability of the w phase is affected by differences in the sample pressure environment; and (4) a short term laser-heating of Ti lowers the alpha-to-omega transition pressure. Possible transition mechanisms are discussed in the light of the present results, which clearly demonstrated the influence of uniaxial stress in the alpha-to-omega transition.