Effect of sintering temperature on the microstructure and mechanical properties of Ti50Ni50 and Ti47Ni47Al6 intermetallic alloys

Ti50Ni50 and Ti47Ni47Al6 intermetallic alloys were prepared by the two-step sintering, and the effect of sintering temperature on the microstructure and mechanical properties of the alloys were investigated by DSC, XRD, OM, SEM, EDS and mechanical tests. The results show that the microstructure of Ti50Ni50 sintered at 1080 °C consisted of NiTi matrix, strengthening phases Ti2Ni, Ni3Ti and some pores. The porosity and the amount of Ti2Ni of Ti47Ni47Al6 alloy increased, while the amount of Ni3Ti decreased. As the sintering temperature increased to 1180 °C, Ni4Ti3(Al) appeared and distributed mainly along grain boundaries, and the porosity and the size of pores decreased. With the temperature further increasing to 1230 °C, the porosity changed insignificantly, but some larger pores were observed in the alloy. The microhardness and flexural strength of Ti50Ni50 sintered at 1080 °C were 234 Hv and 257 MPa respectively, and these of Ti47Ni47Al6 alloy increased to 321 Hv and 364 MPa respectively. The microhardness and flexural strength of the alloy sintered at 1180 °C increased significantly, while decreased slightly at the temperature of 1230 °C. All the samples of Ti50Ni50 and Ti47Ni47Al6 alloys exhibited typical brittle fracture features.