Manufacturing and characterization of Nitinol shape memory alloy: A comprehensive study

Abstract

Nitinol-shaped memory alloy is a superplastic alloy that can return to its pre-deformed shape when heated. Different additives and manufacturing techniques resulted in different alloy characteristics. This study aims to manufacture three different concentrations of nitinol alloy using the sintering technique to expose these alloy characteristics. The alloys were manufactured using sintering techniques followed by melting in an argon atmosphere to prevent oxidation. The procedure includes preparing three concentrations of raw materials: NiTi of (45% Ti + 55% Ni), NiTiCu of (45% Ti + 35% Ni + 20% Cu), and NiTiAl of (35% Ti + 45% Ni + 20% Al), mixing them and sintering them, first directly and second after compressing them under five tons pressure, and examining their properties. Structural and thermal properties were analyzed through X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), and differential scanning calorimeter (DSC). The results demonstrated the influence of alloying elements on the micro-structure, density, and phase transformation temperatures, which are critical for potential applications in various industries. It was found that the manufactured nickel titanium alloy shows a phase of heating transformation temperature of austenite phase starting (As) at 60.87°C and austenite phase finishing (Af) at 75.40 °C, the NiTiCu alloy shows a phase of heating transformation temperature of As at 60.57°C and Af at 69.69°C, and the NiTiAl alloy shows a phase of heating transformation temperature of As at 64.10°C and Af at 75.03°C. The study findings indicate that the addition of copper and aluminum alters the thermal and structural characteristics of the Nitinol alloys, providing insights into their performance for specific applications.