Research on mesoscopic damage evolution models of TC4 titanium alloy under hot deformed process

Based on the mesoscopic damage evolution model of Gurson-Tvergaard-Needleman (GTN), the fracture experimental of uniaxial tensile and shear was carried out at high temperatures 720-800degree celsius. The hot deformation behavior, microstructure, damage evolution and fracture mechanism were analyzed. The result indicated that the nucleation of initial deformation voids mainly appeared in the phase boundary and the secondary a phase matrix, this is due to the stress concentration caused by the inhomogeneity of plastic deformation. However, the conditions of high temperature and low strain rate deformation would promote dynamic recrystallization (DRX) and alleviate the stress concentration, hinder the void growth and polymerization. Based on the research results, the GTN shear modified model was established, which considered the influence of high temperature, and the parameters of the damage model were modified by response surface method and finite element reverse calibration method. By comparing the simulation results with the experimental results, it is found that the shear damage model can accurately predict the high temperature fracture of titanium alloy and reflect the mesoscopic mechanism.