Effects of annealing temperature on microstructures and shape memory effect of Ti-19Zr-11Nb-2Ta alloy sheets

Abstract

The effects of annealing temperature on the microstructures, mechanical properties and shape memory effect of Ti-19Zr-11Nb-2Ta alloy sheets have been investigated. The X-ray diffraction results show that the as-received Ti-19Zr-11Nb-2Ta alloy and those annealed between 873 K and 1073 K are composed of single α″-martensite. The recrystallization temperature of the alloy is between 823 K and 873 K indicated by the optical morphologies, and the thickness of martensite variants increases with the elevating of annealing temperature as detected by transmission electron microscopy (TEM) observations. The reverse martensitic transformation start temperature (AS) slightly increases after annealing above 873 K. The as-received alloy exhibits elongation of only 4.3%, and the plasticity is remarkably improved after annealing above 873 K. The alloy annealed at 873 K exhibits the largest elongation of 21.2% and a maximum shape memory strain of 2.7% among all the samples corresponding to an ultimate tensile strength of 607 MPa.