Microstructure and shape memory effect of Ti-20Zr-10Nb alloy

The microstructure, martensitic transformation behavior and shape memory effect of Ti-20Zr-10Nb shape memory alloy have been studied by X-ray diffraction (XRD), optical microscopy (OM) and transmission electron microscopy (TEM) observation, differential scanning calorimetry (DSC) and tensile stress-strain measurements. The results show that the recrystallization occurs in the cold rolled Ti-20Zr-10Nb alloy by annealing at 600 °C and the grain size goes up with the increasing annealing temperature up to 800 °C. The Ti-20Zr-10Nb alloy is primarily composed of α″ martensite and a small amount of ω phase which appears after annealing. A reverse martensite transformation temperature higher than 500 °C upon heating has been detected for the Ti-20Zr-10Nb alloy annealed at 600 °C, but no obvious exothermic behavior can be found upon cooling. The tensile strength and the failure strain of the alloy are measured to be 542 MPa and 13.1%, respectively, associated with a maximum shape recovery strain of about 2.5%.