Effect of heat treatment on transformation behavior in CuAlNb shape-memory alloys with high transformation temperatures

CuAlNb shape memory alloy with 1.7% Nb ws prepared by using induction melting furnace under argon atmosphere. Their microstructure, phase transformation temperature, mechanical properties and thermal cycling properties were studied as a function of heat treatment process. It was found that the grain size decreases with decreasing quenching temperature. The phase transformation temperature of A→M is almost unchanged, whereas the phase transformation latent heat increases significantly with the increase of quenching temperature. The mechanical properties of the CuAlNb alloy are remarkably changed by heat treatment. After quenching from 1023 K into ice water, the alloy shows a tensile strength of about 950MPa with elongation of about 8.3%, and the maximum recovery rate of about 73.3%. In addition, step quenching treatment improves the thermal behavior of the CuAlNb alloy.