Influence of Alloying Element Addition on Cu–Al–Ni High-Temperature Shape Memory Alloy without Second Phase Formation

Abstract

In this study, the effects of rare earth Gd and Fe elements on the microstructure, the mechanical properties and the shape memory effect of Cu–11.9Al–3.8Ni high-temperature shape memory alloy were investigated by optical microscopy, scanning electron microscopy, X-ray diffraction and compression test. The microstructure observation results showed that both Cu–11.9Al–3.8Ni–0.2Gd and Cu–11.9Al–3.8Ni–2.0Fe–0.2Gd alloys displayed the fine grain and single-phase $$\beta^{\prime}_{1}$$ martensite, and their grain size was about several hundred microns, one order of the magnitude smaller than that of Cu–11.9Al–3.8Ni alloy. The compression test results proved that the mechanical properties of Cu–11.9Al–3.8Ni alloy were dramatically improved by alloying element additions due to grain refinement and solid solution strengthening, and the compressive fracture strains of Cu–11.9Al–3.8Ni–0.2Gd and Cu–11.9Al–3.8Ni–2.0Fe–0.2Gd were 12.0% and 17.8%, respectively. When the pre-strain was 10%, the reversible strains of 5.4% and 5.9% were obtained for Cu–11.9Al–3.8Ni–0.2Gd and Cu–11.9Al–3.8Ni–2.0Fe–0.2Gd alloys after being heated to 500 °C for 1 min, and the obvious two-way shape memory effect was also observed.