Cu-based high-temperature shape-memory alloys and their thermal stability

The newly developed CuAlNb, CuAlAg, CuAlCo and CuAlZr high temperature shape memory alloys are briefly reported. It was found in CuAlNb shape memory alloys that the phase transformation temperature of A→M is near 573 K, which almost keeps unchanged with Nb content up to 1.7wt.%. The tensile strength and the elongation of CuAlNb alloy containing 1.7wt.% Nb are 958MPa and 8.3%, respectively, and the maximum recovery rate of 73.3% is obtained with 5% prestrain. The martensitic transformation temperatures are in the range of 549∼-509K for the CuAlAg alloy with Ag contants 3∼-5wt.%, and the Ag addition effectively increases the stability of the martensitic transformation at high temperature. But the plasticity is poor for the polycrystalline CuAlAg alloy. The CuAlCo and CuAlZr alloys tested exhibit martensitic transformation temperatures higher than 490K. The CuAlCo alloy shows a moderate thermal stability compared with CuAlZr alloy. The former can experience five thermal cycles in the present experiment, but the latter exhibits no martensitic transformation in the second thermal cycle.