Enhanced mechanical property in molybdenum-rhenium alloy via high-temperature aging

Embrittlement induced by recrystallization is a common issue in Mo and Mo-based alloys, as the enrichment of trace elements (such as oxygen) weakens the strength of grain boundaries, leading to brittle intergranular fracture. However, this phenomenon is absent in the recrystallized Mo-47.5Re (wt%) alloy. In this study, high-temperature aging (1600 ℃) was conducted on as-forged Mo-47.5Re alloy, and the microstructures and mechanical properties of the aged samples were characterized at different durations of 0.5 h, 2 h, and 100 h. The average size of recrystallized grains increases sharply as the duration rises from 0.5 h to 2 h and stabilizes as the duration further increases. This stability in grain size during thermal aging is attributed to the pinning of grain boundaries by precipitated particles. The segregation of Re at the grain boundaries takes place in the as-forged sample, and is further enhanced in the recrystallized samples. σ phases gradually precipitate along the grain boundaries during annealing with total volume fraction approximately to 4.65 %. Good cohesion between the σ phases and the matrix results in a combination of high strength, good ductility, and work-hardening ability, yielding excellent comprehensive mechanical properties.