Microstructure Evolution of a Multifunctional Titanium Alloy

Abstract

To optimize both mechanical and functional properties of multifunctional titanium alloys via grain refinement, an example of such alloys termed as Ti2448 is adopted to investigate its microstructure evolution and strain rate sensitivity by compression in the single b-phase field. The results show that flow stress and strain rate follow a bilinear relation, which is in sharp contrast with other metallic materials exhibiting a monotonic linearity. Below the critical strain of 1 s -1 , the alloy has a normal strain rate sensitivity factor of 0.265. Above the critical value, its hardening rate is ultra-low with a factor of 0.03. Inspite of ultra-low hardening, the alloy is plastic stable under the tested conditions. With the aid of electron back-scattering diffraction and transmission electron microscopy analyses, microstructure evolution via several mechanisms such as dynamic recovery and recrystallization is evaluated by quantitative measurements of grain misorientation and its distribution, sub-grain formation, and localized grain refinement. These results are helpful to obtain the homogenous ultrafine-grained alloy by multi-step thermomechanical processing.