Phase transformation and microstructure evolution of the deformed Ti-30Zr-5Nb shape memory alloy

The phase transformation and microstructures of the deformed Ti-30Zr-5Nb shape memory alloy were investigated. The X-ray diffraction measurements indicated that the Ti-30Zr-5Nb alloy was composed of a single orthorhombic α″-martensite phase. The alloy exhibited one yielding behavior in the tensile test, with a critical stress of ~600MPa and a tensile strain of approximately 15%. A shape memory recovery accompanied by a permanent strain was exhibited in the deformed alloys when heated at 873K. The permanent strain increased with increasing pre-strain. The microstructure evolution of the deformed alloy was investigated by transmission electron microscopy. The results showed that the martensite reorientation occurred and the dislocations were generated during deformation. The alloy displayed a reversible martensite transformation start temperature as high as 763K. However, no strain-induced martensite stabilization was found in the deformed alloy with different pre-strain levels, potentially because the large chemical energy of the Ti-30Zr-5Nb alloy depressed the effects of the elastic energy and the dissipative energy. •Ti-30Zr-5Nb alloy is composed of single orthorhombic α″-martensite phase with Ms of 721K.•No martensite stabilization has been found in Ti-30Zr-5Nb alloy with different pre-strain.•Ti-30Zr-5Nb shows the maximum shape memory effect of 2.75% with a pre-strain of 8%.