Microstructure, mechanical property and oxidation property in Ni3Si-Ni3Ti-Ni3Nb multi-phase intermetallic alloys

Microstructure, high-temperature compressive and tensile deformation, and oxidation property of multi-phase intermetallic alloys, which were based on the Ni3Si-Ni3Ti-Ni3Nb pseudo-ternary alloy system and composed of L12, D024 and D0a phases, were investigated. The microstructures of these multi-phase intermetallic alloys were largely dependent on alloy composition. The Widmansttaten-like Ni3Ti(D024) phase was precipitated from L12 matrix by a solid-state reaction, accompanied with a certain orientation relationship and habit plane. The tensile stress as well as the tensile elongation of these multi-phase alloys increased with increasing Si content, i.e. the volume fraction of L12 phase in the wide range of test temperatures. Fifty parts per million boron addition to these multi-phase intermetallic alloys resulted in increased tensile stress and tensile elongation. It was found that the multi-phase intermetallic alloy with a high Si content had good oxidation resistance, accompanied with a continuous silicate layer. From an overall evaluation of the properties examined, it was shown that the multi-phase intermetallic alloy that had a high Si content and was composed of L12 matrix dispersed by D024 and D0a phases had the most favorable properties as high-temperature mechanical and chemical materials.