Improvements in the Superelasticity and Change in Deformation Mode of β-Type TiNb24Zr2 Alloys Caused by Aging Treatments

Abstract

QIANG LI, MITSUO NIINOMI, MASAAKI NAKAI, ZHENDUO CUI, SHENGLI ZHU, and XIANJIN YANG The superelasticity and deformation behaviors of b-type TiNb 24 Zr 2 subjected to aging treatment were investigated in this study. As the aging time increased, the precipitation of isothermal x phase was found to restrain the formations of twinning and stress-induced a¢¢ martensite. The superelastic recovery of the sample first improves and then deteriorates with extended aging times. A maximum and stable superelastic recovery of 4.3 pct is obtained for an aging time of 7.2 ks.

Non-Monotonic Aging Temperature Dependence of Superelasticity of Ti₇₂Nb₁₅Zr₁₀Al₃ Quaternary Alloys

“…Li et al reported that the volume of ½ iso phase of TiNb 24 Zr 2 alloy is increased with increasing aging time in specimens aged at 573 K for 1.8 to 18 ks. 30) The crucial aging temperatures and period in this study is between 453 and 553 K for 3.6 ks, which is a lower temperature range than the temperature which Li et al used, and a similar aging period. Thus, we expect that the precipitation of ½ iso phase in Ti 72 Nb 15 Zr 10 Al 3 alloy under the aging conditions in this study is also at the nucleation and growth stage.…”

Effect of Al Addition on Superelastic Properties of Aged Ti–Nb–Zr–Al Quaternary Alloys

“…Martensitic transformation temperature and reverse martensitic transformation temperature of ¢-Ti alloys depends on the composition of the ¢-Ti phase and the morphology of the ½ phase often precipitating in the ¢-Ti phase. 3,13,14,42) It has been also reported that the ½ phase was suppressed by Al addition. 39) TEM bright field images taken along [110] ¢ orientation were shown in Fig.…”

“…Li et al has reported that the first yielding stress (· M ) remain stable at 380 MPa in TiNb 24 Zr 2 alloy aged at 573 K for 7.2, 10.8 and 14.4 ks. 14) They described this phenomena is related with the balance of two phenomena. One is suppression of ¢ matrix extent and the other is increasing the amount of ¢ stabilizing elements.…”

Titanium Alloys for Biomedical Applications

“…Both the shape-memory functionality and strength of Ni-free β-type titanium alloys can be improved through heat treatment. For example, in Ti-6Mo-8Al (mol%), an increase in strength and complete shape recovery can be achieved through low-temperature aging at 773 K, during which fi ne ω-phase precipitates form homogenously, followed by high-temperature aging at 1,023 K, during which the fi ne α-phase precipitates on the previously precipitated ω-phase, and further high-temperature aging at 1,123 K, during which the ω-phase disappears [ 100 ]. For Ti-24Nb-2Zr (at%) with a simple aging treatment at 573 K, the super-elastic performance fi rst improves, but then deteriorates with extended aging time, as shown in Fig.…”