Low temperature superplasticity of submicrocrystalline titanium alloys

Severe plastic deformation at temperatures below 0.4...0.5Tm was used to obtain submicrocrystalline (SMC) structure in pure titanium and titanium alloys Ti-6.7Al-4.7/Mo and Ti-11Mo-5.5Sn-4.2Zr. The structural studies showed that the density of titanium and its alloys in the SMC condition was less that in the coarse grained (CG) one. This change is connected with the presence of less-density intercrystalline regions. Low temperature superplasticity was studied in the temperature range 450...575 degrees C. A considerable dependence of ductility on alloy composition was shown. The calculated value of apparent activation energy of the Ti-6.7Al-4.7Mo was equal to 315 kJ/mol at n=2.3, that being higher than during superplastic (SP) deformation of the alloy with usual microstructure.