Characterization of Structural Properties of NiTi Alloys Synthesized by Powder Metallurgy Method

Abstract

NiTi alloys have shape memory, super elasticity, high impact damping capacity, high corrosion resistance and biocompatibility. Powders with different shapes, sizes and packaging properties can be produced with powder metallurgy methods as high performance, high dimensional sensitivity, chemical composition can be controlled and porous materials. For this purpose, mechanical alloying process was carried out using Ni and Ti powders in equal moles. 58.7g of Ni and 47.9 g of Ti were taken one mole and 0.14 mol of Ni and Ti powders were used in the first three of the experiments. To reduce dust consumption, 0.047 moles of Ni and Ti powders were used in subsequent experiments and it was aimed to obtain a NiTi alloy. The effects of the change of rotational speed and grinding time on alloying were investigated using a planetary grinder. XRD (X-Ray Diffraction) was used for phase analysis. In the planetary grinding device used, the effects of changing the rotation speed and changing the alloying time on alloying were examined. X-ray diffraction graphs and scanning electron microscopy images of NiTi powders synthesized in various parameters were taken and their structural properties were interpreted. In this study, 12 experiments were carried out. The Ti₂Ni phase was not found under 300 rpm and 200 rpm under 40 hours. In 40-hour and 80-hour experiments, peak formation overlapping with Ti₂Ni phase was observed. The Ti₂Ni phase was not found in 10 and 20 hours of experiments at 400 rpm. It was observed that crack formation started in large grains at 400 rpm speed. It was concluded that the experiment period must be at least 40 hours for alloying to take place.