Powder Metallurgy Fabrication of Porous 51(at.%)Ni-Ti Shape Memory Alloys for Biomedical Applications

The effect of time and temperature on the microwave sintering of 51(at.%)Ni-Ti shape memory alloys (SMAs) was investigated in the current research. Furthermore, the microstructure, mechanical properties, and bio-corrosion properties were analyzed based on the sintering conditions. The results revealed that the sintering condition of 700 degrees C for 15 min produced a part with coherent surface survey that does not exhibit gross defects. Increasing the sintering time and temperature created defects on the outer surface, while reducing the temperature to 550 degrees C severely affected the mechanical properties. The microstructure of these samples showed two regions of Ni-rich region and Ti-rich region between them Ti2Ni, NiTi, and Ni3Ti phases. The differential scanning calorimeter (DSC) curves of Ni-Ti samples exhibited a multi-step phase transformation B19'-R-B2 during heating and cooling. An increase in the sintering temperature from 550 to 700 degrees C was found to increase the fracture strength significantly and decreased the fracture strain slightly. Reducing the sintering temperature from 700 to 550 degrees C severely affected the corrosion behaviors of 51%Ni-Ti SMAs. This research aims to select the optimum parameters to produce Ni-Ti alloys with desired microstructure, mechanical properties, and corrosion behaviors for biomedical applications.