Microstructure evolution and mechanical property improvement of Ti-542 alloy under cryorolling-based annealing designs

Abstract

The cryorolling at liquid nitrogen temperature and recrystallization annealing treatment (CRAT) has been applied on the Ti-542 metastable β titanium alloy, aiming to address the strength-plasticity inversion issue. The results show that CRAT can significantly modify the microstructure, not only by reducing the average grain size by nearly one order of magnitude, but also by creating a mixed-grain structure when annealing near the phase transformation temperature. The deformation mechanism during cryorolling is mainly governed by {332}〈113〉 twinning, and annealing at 770–780 °C can precisely balance the proportion between detwinning and grain refinement. The strength-plasticity matching of the alloy after CRAT has been remarkably enhanced, where the sample can exhibit a tensile strength of 1138.4 MPa (increased by 27% than the samples without CRAT) and a fracture elongation of 23.1%, overcoming the strength-plasticity trade-off limitation. The deformation behavior analysis by in situ High Energy X-Ray Diffraction (HEXRD) shows that the excellent performance of the alloy arises from the synergistic effects of the coarse-grain/fine-grain structure and advantage/random orientation distribution, which not only enhances the cooperative deformation characteristics but also improves the work hardening capacity. This research is expected to provide a theoretical basis and practical guidelines for the microstructure design and property control of new metastable β titanium alloys.