Microstructure evolution in pure titanium during warm deformation by combined rolling processes

摘要

The constitutive analysis of stress-strain state by the finite element method was carried out by using the LS-DYNA software for the axis and surface points of rods of commercially pure titanium VT1-0, which were thermomechanically treated by consequent screw rolling and shape rolling at temperatures of 723 and 623 K, respectively. The features of plastic strain distribution in cross section of workpiece, the strain rate evolution in the axis and surface points and the amount of adiabatic heat were considered. The stress state was revealed in terms of stress state factors and directing stress tensors during processing time. The microstructure evolution was studied by the electron back-scattering diffraction method and analyzed using the TSL OIM software. The mechanisms of grain refinement, which were controlled by dynamic recrystallization, and the effect of nonhomogeneous stress-strain state in the axis and surface areas were discussed based on the analysis of strain hardening mechanisms, Schmidt factor and JMAK equations.