Effect of sintering temperature on microstructure, phase evolution, thermo-mechanical properties of spark plasma sintering of NiTi alloy

This study examines the significant effects of sintering temperatures on the microstructure and the thermal, mechanical, and dynamic mechanical properties of NiTi alloys. The compaction of polycrystalline Ni50Ti50 (at. %) powders via spark plasma sintering (SPS) at various temperatures. The starting powder, with a particle size of 20 to 63 mu m, was compacted at a fixed pressure of 50 MPa. Our findings indicate that the consolidated alloy exhibits stable phases of NiTi, such as austenite and martensite, at different sintering temperatures. Notably, both compactness and hardness improve as the sintering temperature increases. Higher temperatures lead to decreased porosity, resulting in a denser structure with a chemical composition of Ni47.1Ti52.9 (at.%). The grain size distribution also narrows with increased temperatures, highlighting microstructural evolution. Moreover, the samples displayed remarkable shape memory behavior and exceptional thermo-mechanical properties, achieving a maximum compactness of 99.8 % at 1150 degrees C. This research thoroughly investigates the influence of sintering temperature on microstructural characteristics, phase transformations, and shape memory behavior, underscoring the potential of NiTi alloys for various applications.