Characterization of NiTi and NiTiCu Porous Shape Memory Alloys Prepared by Powder Metallurgy (Part I)

In this paper, the effect of compacting pressure (150–450 MPa) and copper (Cu) additions (2.5, 5, 7.5 and 10 wt%) on the microstructure and physical properties of NiTi-based shape memory alloys prepared by powder metallurgy is studied. Many characterization techniques were employed in this study such as X-ray diffraction method and scanning electron microscope. The chemical composition of the prepared alloys and microstructure was achieved by using scanning electron microscope equipped with EDS. Differential scanning calorimetric is utilized to measure the transformation temperature of the prepared alloys. Several physical tests such as particle size distribution measurements, density and porosity of green compacted samples and density and porosity after sintering are achieved. XRD test shows that the master sintered samples consist of three phases at room temperature: NiTi monoclinic phase, NiTi cubic phase and Ni3Ti hexagonal phase. Furthermore, (CuNi2Ti) intermetallic compound is appeared in the samples with 2.5, 5, 7.5 and 10 wt% of Cu. According to the results, it was found that compacting pressure has an essential effect on the decreases in porosity percentage and the results show that (Cu) additions increase porosity percentage in all weight percentages of additives.