Effects of short time electric pulse heat treatment on microstructures and mechanical properties of hot-rolled Ti–6Al–4V alloy

Abstract

Effects of electric pulse heat (EPH) treatment on microstructures and mechanical properties of hot-rolled Ti–6Al–4V alloy are investigated. It is interesting to find that, the original bimodal microstructure of hot-rolled Ti–6Al–4V alloy is transformed to the typical lamellar microstructure within several minutes, and the minutes spent for accomplishing microstructure transformation become less with the increased heat treatment temperature. Before the formation of lamellar microstructure, recovery and recrystallization happen to the original bimodal microstructure; after the formation of lamellar microstructure, the average grain size shows an increasing tendency with the increased temperature and maintaining time. Quasi-static compression test results show that, the critical failure strain of the recrystallized microstructure is improved compared with the hot-rolled Ti–6Al–4V alloy, once the recrystallized microstructure is transformed to lamellar microstructure, the critical failure strain shows a decreasing tendency. Dynamic compression test results show that, the susceptibility to adiabatic shear bands (ASBs) of the hot-rolled Ti–6Al–4V alloy is obviously declined after EPH treatment, particularly the initially transformed lamellar microstructure exhibits the lowest susceptibility to ASBs, owing to the deformation zones around the main ASB and the bifurcation of the main ASB. The alloy EPH-treated at 800 °C for 20 min with the smallest grain size of 200 μm shows the best dynamic ductility.