Ｔｉ‐Ｎｉ系アモルファス合金粉末のＨＩＰ焼結

Abstract

Amorphous Ti50-Ni50 powders prepared by MA were sintered by HIP above 700°C to obtain the compacts with non-equilibrium phases.The x-ray diffraction peaks of the specimen obtained at 700°C were relatively weak and broad.On the other hand, the specimen obtained at 900°C consisted of TiNi, Ti2Ni and Ni3Ti with relatively sharp peaks in the x-ray diffraction pattem.The compacts obtained may be in the non-equilibrium states leading to the equilibrium phase of TiNi.The most amorphous like compact was obtained at 700°C for lhr under 200MPa and its density was 6.2g/cm3 corresponding to 94% of the density obtained at 900°C.The grains in the compacts obtained at 700-800°C maintained the shape formed by MA, while the micro structure obtained at 900°C was largely different.The Vickers hardness of the compact obtained at 700°C was 900Hv compared with 800Hv at 900°C.The electric resistivity of the compact obtained at 700°C was 2 times higher than that of TiNi alloy.Anodic polarization curves of the compacts indicated high corrosion resistance in the compact obtained at low Hipping temperature.It was concluded that the high density compact of Ti-Ni was obtained keeping some properties of amorphous metal using low temperature HIP of amorphous Ti-Ni powders.