Effect of Alloying of Raw Materials and Sintering Method on Performance of NiTi Alloy

Nickel titanium alloys are widely used in various fields due to its excellent shape memory effect, superelasticity, and good biocompatibility. This paper studies the effect of raw material powder alloying and sintering methods on sintering substance structure and properties. With nickel/titanium mixed powder and nickel-titanium alloy powder as raw materials, green bodies were obtained by gel casting forming and NiTi alloy was obtained through different sintering methods. By using X-ray diffractometer and scanning electron microscope, this paper studied the structure and properties of raw material powder and sintering substance. Results show that NiTi alloy prepared by NiTi alloy powder contains larger amount of NiTi phase in the structure compared with nickel-titanium mixed powder. The alloy was sintered at 1050℃ for 4 h under hot isostatic pressing, and the sintered pressureat is 25 MP. The alloy with a relative density of 91.5% and a density of 5.9 g/cm³ was prepared. The average hardness of the alloy produced by hot isostatic pressing is 226.2 HV, which is about 33.6 HV higher than that of the vacuum sintered alloy. Hot isostatic pressing sintering can promote the densification of the alloy during sintering and greatly increase the density of NiTi alloy prepared by gel casting.