Characterization and corrosion behavior of NiTi–Ti2Ni–Ni3Ti multiphase intermetallics produced by vacuum sintering

An in-situ synthesis method was employed to produce NiTi–Ti2Ni–Ni3Ti multiphase intermetallics. In this regard, the amorphous/nanocrystalline Ni–Ti powders were sintered at 1300 °C for 2 hrs to obtain Ni–Ti alloys with dense structure. Tafel polarization tests were employed to study corrosion behavior of multiphase materials in 3.5% NaCl and 0.1 M H2SO4 corrosive media. The results indicated that the microstructure of sintered samples consists of NiTi(Fe) and Ti2Ni/Ti4Ni2Ox phases embedded in a Ni3Ti matrix. The synthesized multiphase materials had microhardness up to 873 HV1 kg.Further investigations showed the corrosion performance of multiphase samples in 3.5% NaCl solution was inferior to that of wrought NiTi alloy. In contrast, the corrosion resistance of multiphase samples in 0.1 M H2SO4 solution was comparable to that of wrought NiTi alloy.

► NiTi–Ti2Ni–Ni3Ti multiphase intermetallics were produced by vacuum sintering.
► NiTi–Ti2Ni–Ni3Ti multiphase intermetallics showed high microhardness values.
► Sintered samples showed good corrosion performance in both NaCl and H2SO4 media.
► The chloride ion adsorption was responsible for pitting corrosion of sintered NiTi.