Strain induced martensite stabilization and shape memory effect of Ti-20Zr-10Nb-4Ta alloy

The phase transformation, the microstructure and the shape memory effect of the Ti-20Zr-10Nb-4Ta alloy are investigated. The X-ray diffraction measurements indicated that the alloy is composed of single orthorhombic α″-martensite. The alloy showed a two-stage yielding behavior upon tension at 0.5% and 6% strain with a yield stress of 215 MPa and 565 MPa, respectively. The strain induced martensite stabilization was identified because the reverse martensite transformation start temperature of the alloy increases from 348 to 405 K, with the pre-strain increasing from 0% to 8%. This can be ascribed to the martensite reorientation that occurred at a low strain level and the dislocations formed at a large strain level. The maximum shape memory strain is 3.3% in the Ti-20Zr-10Nb-4Ta alloy.