H. Hosoda, T. Inamura, K. Wakashima, Tokyo Institute of Technology, Yokohama, Japan; H. Y. Kim, S. Miyazaki, University of Tsukuba, Tsukuba, Japan
This paper describes recent achievements of Ti-Nb-Al shape memory / superelastic alloys which have been developed by the authors’ group. The alloys are composed of nontoxic elements only, and a typical superelastic composition is Ti-24mol%Nb-3mol%Al of which martensitic transformation start temperature (Ms) and austenite transformation finish temperature (Af) are about 260K and 290K, respectively. The superelastic strain, which includes elastic and transformation strains, of the alloy reaches 6% at room temperature. By a dynamic mechanical analysis, this alloy exhibits low modulus and high damping: the lowest Young’s modulus E < 30GPa and the largest internal friction Q-1 > 0.1. The alloy exhibits superior cold workability; more than 99% cold rolling can be done without intermediate annealing. Now thin plates with less than 0.1mm thickness and wires with less than 0.2mm diameter are produced by cold work only. Due to such good superelasticity, workability, low Young’s modulus and good corrosion resistance, Ti-Nb-Al alloys are suitable for biomedical applications such as bone plates, stents and catheters. In this paper, effects of chemical composition, quaternary addition, cold rolling, heat treatment, texture formation on shape memory properties are summarized.
Summary: This paper describes recent achievements of Ti-Nb-Al shape memory / superelastic alloys which have been developed by the authors’ group. The alloys are composed of nontoxic elements only, and a typical superelastic composition is Ti-24mol%Nb-3mol%Al of which martensitic transformation start temperature (
Ms) and austenite transformation finish temperature (
Af) are about 260K and 290K, respectively. The superelastic strain, which includes elastic and transformation strains, of the alloy reaches 6% at room temperature. By a dynamic mechanical analysis, this alloy exhibits low modulus and high damping: the lowest Young’s modulus
E < 30GPa and the largest internal friction
Q-1 > 0.1. The alloy exhibits superior cold workability; more than 99% cold rolling can be done without intermediate annealing. Now thin plates with less than 0.1mm thickness and wires with less than 0.2mm diameter are produced by cold work only. Due to such good superelasticity, workability, low Young’s modulus and good corrosion resistance, Ti-Nb-Al alloys are suitable for biomedical applications such as bone plates, stents and catheters. In this paper, effects of chemical composition, quaternary addition, cold rolling, heat treatment, texture formation on shape memory properties are summarized.
