Micromechanical study of formation and evolution of martensite for Cu-Al-Ni single crystal by moiré interferometry

The basic properties of pseudoelasticity of Cu-Al-Ni single crystal are studied to analyze the morphology associated with the formation and evolution of martensite and the shape memory recovery process at different temperatures. Use is made of a multifunctional macro-micro moiré interferometry measurement system. The β₁ to β₁^′ phase changes are identified with the stress-induced transformation of a Cu-13.7%Al-4.18%Ni (wt%) alloy. The invariant plane between the martensite and the parent phase is shown directly by fringe patterns. It is found that martensite appears in the shape of bands or thin plates on the surface of the specimen. The formation of martensite is a very rapid process and martensite 'jumps' out until the specimen is completely transformed into a single variant. The results reveal the mechanism and process of stress-type and temperature-induced martensitic transformation.