Strengthening and dynamic recrystallization mediated by Si-alloying in a refractory high entropy alloy

Refractory high entropy alloys (RHEAs) are increasingly attractive for potential high temperature applications. To further optimize the mechanical properties, here we introduce intermetallic silicides into a RHEA (TaMo_0.5NbZrTi_1.5Al_0.1) via Si alloying. Interdendritic eutectics composed of body-center cubic (bcc) matrix and hexagonal silicides are formed after solidification. The alloying of Si facilitates substantial grain refinement and formation of intergranular silicides upon annealing at 1300 °C for 48 h. Owing to such microstructure modifications, the compressive strengths of the Si-containing alloy at room and elevated (1200 °C) temperatures are effectively improved. The alloying of Si also promotes transgranular fracture upon compressive testing at room temperature. Dynamic recrystallization (DRX) is evidently accelerated in the Si-containing alloy during compression at 1200 °C, and necklace-like microstructures are generated with the formation of small-sized grains along original grain boundaries. The work suggests that Si-alloying can be an effective approach for significantly enhancing strength and deformation compatibility of RHEAs at room and elevated temperatures by enabling the formation of fine silicides and the additional solute effects.