Influence of Thermomechanical Processing on Microstructure and Mechanical Properties of MoNbTaW Refractory High-Entropy Alloy

In the present work, a refractory high-entropy alloy of the composition MoNbTaW has been synthesized by vacuum arc melting starting with elemental powders. The alloy formed as a solid solution with the body-centered cubic crystal structure. Thermomechanical processing was performed, and the sizeable compressive strain induced during this step aided in removing the dendritic microstructure in the as-cast sample. Further homogenization at 1400 °C for 20 h showed partial recrystallization (as studied by Electron Backscatter Diffraction). The sample subjected to thermomechanical processing followed by homogenization exhibited higher hardness than similar refractory high-entropy alloys in the literature. Detailed estimations on probable strengthening mechanisms in this system under various processing conditions suggest that solid solution strengthening is the dominant mechanism. The obtained Tabor factor for each processing condition of this alloy is in the range of 2.6–2.9, and these numbers are in close agreement with those observed for various metallic materials, including high-entropy alloys.