Enhanced mechanical properties of a metastable β titanium alloy via optimized thermomechanical processing

An efficient and simple thermomechanical processing is particularly important to obtain homogenous microstructures. In this work, an optimized thermomechanical processing consisting of multiple isothermal compression processing and stress relaxation processing was conducted on a metastable β titanium alloy (Ti–5Al–5Mo–5V–3Cr-0.5Fe). The sample geometry after designed thermomechanical processing maintain the same with the geometry after an unidirectional compression, but with totally different microstructures. The results show that a fully fine equiaxed microstructure with the mean size of 160 nm is obtained after the designed processing. Such fine microstructure has not been reported previously in titanium alloys processed by conventional isothermal compression and annealing. In addition, the yield strength of the sample after designed processing was significantly enhanced. The mobile dislocation slipping and stacking faults induced shear are the main mechanisms behind stress relaxation stage in thermomechanical processing. This work can provide an effectively novel thermomechanical processing to optimize the mechanical properties.