Strengthening by Addition of Refractory Elements to Ni3(Si,Ti) Intermetallic Alloys

Abstract

Two atomic percent of refractory elements Ta and Re were added to an L12-type Ni3(Si,Ti) intermetallic alloy in two methods of substituting for Ni or Ti. Alloying effect and substitutional behavior of the refractory elements on microstructure and mechanical properties were investigated. All the alloys were doped with 50 wt.ppm boron to suppress intergranular fracture. The Ta-added Ni3(Si,Ti) alloys showed an entire or almost L12 single-phase microstructure. Their hardness was enhanced due to solid solution hardening which was primarily caused by the atomic size misfit. Also, the yield stress and tensile strength of the alloy where Ta was added by substituting for Ti, increased keeping a high level of tensile elongation. The Re-added Ni3(Si,Ti) alloys showed a two-or three-phase microstructure containing fine Re-rich dispersions. The Re-added alloys exhibited relatively small grain size, and showed significantly high yield stress and ultimate tensile strength with a high level of tensile elongation.