The effect of second-phase dispersions on mechanical property of Ni3Si based multi-phase intermetallic alloys

Using alloys whose initial microstructures are composed of Ni3Si(L12), Ni3Si(L12) + Ni3Ti(D024) and Ni3Si(L12) + Ni3Nb(D0a), aging phenomenon and the associated high-temperature tensile property were investigated. The plate-like Ni3Ti (D024) phase was precipitated from the Ni3Si (L12) matrix at high temperature. It was shown by micro-hardness measurement that age hardening behavior due to the precipitation of the Ni3Ti (D024) phase occurs in all alloys in the temperature range from 923 K to 1323 K. It was however shown by tensile test that the precipitated Ni3Ti (D024) phase is not so much effective in improving the mechanical properties of alloys whose initial microstructures are composed of Ni3Si(L12) + Ni3Nb(D0a) or Ni3Si(L12) + Ni3Ti(D024). In alloys whose initial microstructures are composed of Ni3Si(L12) + Ni3Nb(D0a), a good combination of tensile strength and tensile elongation was found over a wide of test temperature regardless of presence or absence of the precipitated Ni3Ti (D024) phase. It is suggested that the primary coarse Ni3Nb (D0a) phase precipitates are beneficial to improving the mechanical properties.