Investigation of the Texture Evolution and Superelastic Behavior During Annealing in a Ti-Zr-Nb-Sn Biomedical Shape Memory Alloy

Abstract

Texture evolution and superelasticity of an annealed Ti-40Zr-8Nb-2Sn (at.%) shape memory alloy was investigated by X-ray diffraction (XRD), electron back-scattered diffraction (EBSD), and tensile tests in this study. After severe cold rolling at room temperature, the sheet was annealed between 773 and 1173 K. A single beta phase was observed in the alloy specimens annealed between 873 and 1173 K. At 873 K, a microstructure with nonuniform beta grains, grain sizes ranging from 0.3 to 19 mu m, was observed, and the main texture was identified to be {113}beta <(1) over bar(2) over bar1 >(beta). The {001}beta < 110 >(beta) texture was formed at 973 K, and its intensity increased as the annealing temperature increased. At 1173 K, a very strong {001}(beta) < 110 >(beta) texture was formed. Furthermore, the maximum intensity around the < 012 >(beta) direction was obtained in the rolling direction in the specimen annealed at 873 K. The maximum intensity around the < 110 >(beta) direction was obtained in the specimens annealed at 973-1173 K, and it increased as the annealing temperature increased. A maximum recovery strain of 5.5% was achieved in the alloy specimen annealed at 1173 K, which was higher than those in the specimens annealed at 873-1073 K. This is attributed to the strongest {001}(beta) < 110 >(beta) texture that developed at 1173 K as the grains grew after recrystallization.