Influence of pre-strain on inelastic recovery and shape memory property of metastable Ti–10V–2Fe–3Al alloy

The microstructure evolution, inelastic recovery and shape memory effect of the solution treated metastable Ti–10V–2Fe–3Al (Ti-1023) alloy under tensile loading-unloading deformation were investigated. As a consequence of stress-induced martensitic transformation (SIMT) and martensitic reorientation, the tensile stress-strain curve exhibits a pronounced double-yield stress plateau. In addition to the elastic recovery of α" and β phases, an inelastic recovery strain is generated by the reversal of α" martensite. As the pre-strain increases, interactions between differently oriented α" variants result in an increase in internal stress and the formation of defects. This, in conjunction with the plastic deformation of β and α" phases, results in the accumulation of dislocations that impede the reorientation and reversal of α" martensite. The differential scanning calorimetry (DSC) results demonstrate that the onset temperature (A_s) of reverse martensitic transformation increases with pre-strain increasing. Moreover, the volume fraction of α" martensite also increases with pre-strain, resulting in the formation of numerous phase boundaries and grain boundaries, as well as an elevated dislocation density within the martensite, thereby enhancing the stability of the martensite. As the pre-strain increases, the elevated density of dislocations and boundaries, results in a notable diminution of the shape memory effect in the alloy.