The role of deformation in the microstructure, mechanical properties, and shape memory characteristics of Cu-Al-Ni shape memory alloys

Abstract

Due to its potential high-temperature applications, Cu-Al-Ni shape memory alloys have recently attracted much interest. This article attempts to investigate the different percentages of deformation of 1%, 2%, and 4%. on the microstructure, mechanical properties, and shape memory effect of Cu-13wt.% Al-4wt.% Ni shape memory alloys. The findings indicated that the deformed specimen performed much better than the homogenized sample. From microstructural observations, it is seen that the β1′ (18R) and γ1′ (2H) martensite phases as needles- and plates-like morphologies coexisted at different fractions in the undeformed and deformed states. Furthermore, the transformation temperature curves have shifted toward higher transformation temperatures as the deformation percentage increases. The deformed alloy exhibits good mechanical properties with high ultimate tensile strength and ductility after deformation at 2% and 4%, respectively. The microhardness of the deformed samples exhibited the lowest hardness of 247.6 Hv at a 4% deformation percentage. However, it exhibits ductile fracture, including mixed intergranular and transgranular features with linear stress-strain behaviour after applying a 4% deformation percentage. The shape recovery of 94.6% of the original length was achieved when a 2% of the deformation was applied. Because of this, it is reasonable to expect that the mechanical properties and shape-memory attributes of Cu-based SMAs are drastically affected by deformation.