Synthesis and Microstructure Investigation of Ni₄₀Ti₅₀Cu₁₀ Intermetallic Shape Memory Alloys by Self-Propagating Combustion Method

This study concerns the substitution of copper for nickel in the Ni–Ti system in order to obtain a molar ratio of Ni₄₀Ti₅₀Cu₁₀. Effects of preheating temperature were studied to understand the morphology, phase transformation, and microstructure of the samples by using self-propagating high-temperature synthesis. Therefore, three distinct preheating temperatures (230 °C, 320 °C, and 410 °C) were used for the study. The thermochemical calculations performed with FactSage presented similar results with the experimental data in terms of solid–liquid ratios and adiabatic temperature during the reactions. An increase in the preheating temperature very slightly changed the transformation temperature, but it was shown to be insignificant. B2 crystal structure was found as the main phase besides a small amount of martensite, Ti₂Ni(Cu), and Ni(Cu)₂Ti–Ni(Cu)₃Ti by various characterization methods. The monoclinic twinned martensitic (B19′) structure was encountered in transmission electron microscopy analyses. Graphical abstract: [Figure not available: see fulltext.]