Martensitic transformation and shape memory recovery property of Cu72Al26.5Nb1.5 high temperature shape memory alloy

Martensitic transformation and shape memory recovery property of Cu72Al26.5Nb1.5 alloy have been systematically investigated by means of differential scanning calorimeter, X-ray diffraction, transmission electronic microscopy and bending test in this work. The results show that the alloy undergoes one-step martensitic transformation from the monoclinic β′1β′1 to DO3 cubic structure during the process of cooling and heating, and the martensitic transformation starting temperature of the alloy is up to 560 K, indicating the potential application in high temperature environment. TEM observations reveal that the martensites exhibit typical spear-like, plate-like and fork-like morphologies, and most of the martensite variants show self-accommodated state with (0 0 1 8) twin relationship. Two kinds of the substructures of martensites are determined to be (1 2 1 0) twin and (1 1 0) stacking faults for the alloy. Bending tests indicate that the aging time has remarkable influence on the shape recovery ratio of the alloy. The shape recovery ratio firstly decreases and then becomes stable with the aging duration increasing.

Research highlightsThe martensite variants show self-accommodated morphology with (0 0 1 8) twin relationship. (1 2 1 0) twin and (1 1 0) stacking faults substructures are found in the martensite. The shape recovery ratio of the alloy aged in both martensite and austenite state decreases with the aging time increasing in the early stage and then becomes stable.