Characteristics and compressive properties of porous NiTi alloy synthesized by SHS technique

Porous NiTi intermetallic compounds were synthesized from elemental powders by self-propagating high-temperature synthesis (SHS) method. The effects of compaction pressure and preheating temperature on the characteristics and compressive properties were investigated. Microstructure, phase compositions, and mechanical properties were studied by optical microscope, scanning electron microscope (SEM), X-ray diffraction (XRD), energy-dispersive spectrometer (EDS), and compression test, respectively. The experimental results show that compaction pressure and preheating temperature greatly affect porosity, and compressive strength of porous NiTi SMAs. Higher compaction pressures and preheating temperatures result in higher compressive strength and higher compressive strain, but lower porosity. The general porosity of the synthesized porous sample is in the range of 42–58% and the average pore size is between 340 and 500 μm. Pores in the samples are mostly open with an open porosity ratio of 87–98%. The porosity and the compressive strength of the synthesized porous products in this study meet the basic strength requirements of human cancellous bone with corresponding porosity. The main phases in porous NiTi SMA are B2 (NiTi) and B19′ (NiTi) which are the desired phases. NiTi2 and Ni4Ti3 phases are also present in small amounts.