Abstract:

In this article, a novel method of maximum mvalue superplastic deformation (Max m SPD) is presented. It is well known that strainrate sensitivity exponent (m) is a critical parameter for a material, which quantifies its superplasticity level. The higher the m value is, the better the superplasticity of a material will be. The rationale is to maintain the maximum m value in the forming process through simultaneous m value measurement and concurrent deformation strain rate control. Meanwhile the Max m SPD is carried out through a superplastic tensile test of titanium alloy TC11 (Ti₆₅Al₃₅Mo₁₅Zr0₃Si) at high deformation temperature, and the greatest elongation reached at 2 300% at the deformation temperature of 900 ℃. The optical microscope (OM) and transmission electron microscope (TEM) analysis results show that grain-boundary sliding is the mainly deformation pattern of superplastic deformation for titanium alloy TC11, coupled by intracrystalline dislocation sliding. The method of Max m SPD is an effective method to improve the superplasticity of titanium alloys because this method enables completely dynamic recrystallization to take place.

Key words: titanium alloys, superplasticity, deformation, maximum mvalue, deformation mechanism, high temperature tensile