Effect of The Refractory Element Additions on Microstructure and Mechanical Property of Two-phase Intermetallic Alloys Based on The Ni_3Al-Ni_3V Pseudo-binary Alloy System

摘要

Two-phase intermetallic alloys composed of geometrically close packed (GCP) Ni_3Al (Ll_2 phase) and Ni_3V (Do_(22) phase) have attractive mechanical properties at high temperature, and are therefore considered to be used as high temperature structural materials. In this study, the effect of Ta and Re addition on the microstructure and hardness of two-phase intermetallic alloys was investigated. The addition of Ta remarkably enhanced the hardness due to solid solution hardening of the constituent phases. On the other hand, the addition of Re retarded the formation of the two-phase microstructure, resulting in the lowest hardness in the solution treated condition. By aging at 1223 K, the Ni solid solution in the Re added alloy decomposed to Ni_3Al and Ni_3V, accompanied by precipitates of a Re-rich phase. Consequently, the hardness rapidly increased with increasing aging time. Simultaneous addition of Ta and Re induced very fine precipitates of a Re-rich phase after aging, and consequently resulted in a higher hardness than by the addition of Ta or Re alone.