Effect of solution treatments on microstructure and mechanical properties of Ti–6Al–4V alloy hot rolled sheet

Abstract

The solution and aging treatment were carried out with the hot rolled sheet Ti–6Al–4V alloy sheet, and the effects of solution treatments on the microstructure and mechanical properties were mainly studied. In the solution treatment process, α→β→βt transformation occurred. With the increase of solution treatment temperature and time, the α phase gradually changed from long strip to equiaxed morphology, and the fraction of equiaxed α and β phases gradually increased. The bimodal microstructure of αp and βt was obtained during the solution treatments. Among them, βt is mainly composed of high-density nano-needle αs with different orientations, which has a significant contribution to the strength of Ti–6Al–4V alloy. The strength of bimodal microstructure increases with the increase of βt content, but its influence on ductility is complicated. When βt content exceeds a certain amount, it is easy to lead to brittleness. It is found that when the specimens are treated at 930 °C for 60min or 960 °C for 30min, the best strength-ductility matching can be obtained. In this case, the volume fractions of αp and βt are almost equal, and the PSE of Ti–6Al–4V alloy reaches more than 14500 MPa⋅%.