The α→ω Transformation in Titanium-Cobalt Alloys under High-Pressure Torsion
نویسندگان
چکیده
The pressure influence on the α → ω transformation in Ti–Co alloys has been studied during high pressure torsion (HPT). The α→ω allotropic transformation takes place at high pressures in titanium, zirconium and hafnium as well as in their alloys. The transition pressure, the ability of high pressureω-phase to retain after pressure release, and the pressure interval where α andω phases coexist depend on the conditions of high-pressure treatment. During HPT in Bridgeman anvils, the high pressure is combined with shear strain. The presence of shear strain as well as Co addition to Ti decreases the onset of the α→ ω transition from 10.5 GPa (under quasi-hydrostatic conditions) to about 3.5 GPa. The portion ofω-phase after HPT at 7 GPa increases in the following sequence: pure Ti→ Ti–2 wt % Co→ Ti–4 wt % Co→ Ti–4 wt % Fe.
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