Effect of strain reversal on the stress-induced martensitic transformation and tensile properties of a metastable β titanium alloy

In this study, the effect of strain reversal on the evolution of microstructure and mechanical properties was investigated. Metastable beta titanium alloy samples with single beta phase were twisted up to 360 degrees with different strain paths: monotonic torsion (MT) and cyclic forward-reverse torsion (CFRT). The results revealed CFRT with strain reversal accumulated lower dislocation density and less martensitic transformation in comparison with MT under the same accumulative strain. The stress-induced martensitic transformation (SIMT) was retarded by strain reversal and this suppression of martensitic transformation is more pronounced with the decreasing amplitude of strain reversal. It was further observed that CFRT samples with a gradient alpha '' martensite have a higher mechanical property both in strength and ductility than MT samples, which are due to interactions between alpha '' martensite and dislocation slip, especially the kinks of alpha '' martensite. (C) 2019 Elsevier B.V. All rights reserved.