Pressure-induced α→ω transition in titanium metal:: a systematic study of the effects of uniaxial stress

The effects of uniaxial stress on the pressure-induced alpha --> omega transition in pure titanium (Ti) are investigated 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 alpha and omega phases coexist over a rather large pressure range, which depends on the pressure medium employed; (3) the hysteresis and quenchability of the omega phase is affected by differences in the sample pressure environment; and (4) a short-term laser heating of Ti lowers the alpha --> omega transition pressure. Possible transition mechanisms are discussed in the light of the present results, which clearly demonstrate the influence of uniaxial stress in the alpha --> omega transition. (C) 2004 Elsevier B.V. All rights reserved.