Fast and Diverse Phase Evolution in Vconi Medium Entropy Alloy

Abstract

Tuning phase constitution can exert positive influence on mechanical properties, but it is generally considered impractically in compositionally complex alloys due to kinetic limitation. Here we show that fast and diverse phase evolution can be stimulated in VCoNi medium entropy alloy via tensile deformation at various temperatures. While some thermally-induced HCP phase is already presented after annealing, more FCC matrix is transformed to another HCP phase during deformation at 25 °C, which is related to strain accumulation and slight Co segregation. Further increasing the test temperature to 400-600 °C eliminates all the HCP phases but leads to dynamic precipitation of the brittle σ phase. At 700-800 °C, κ and σ phases are formed at temperatures lower than theoretically prediction under the improved diffusivity assisted by the high-density defects. Besides, the impact of the phase evolution on the mechanical behaviors is also discussed.

Keywords: Medium entropy alloy, Temperature, deformation, Phase evolution, mechanical property