Intense research efforts are focused on the development of advanced high-entropy alloys intended for premium aerospace components and other applications, where high strength and good formability are crucial. The mechanical properties of these alloys are closely related to the phase transformation, dislocation evolution, and grain size, and these factors are affected by the deformation temperature. The response of the retained austenite to strain-induced martensitic transformation at various temperatures was studied in an advanced Ti68Nb7Ta3Zr4Mo18 (at.%) high-entropy alloy via molecular dynamics simulation. It was found that the Ti68Nb7Ta3Zr4Mo18 alloy changes from a single crystal to a polycrystal during the tensile process, and the transition of the Ti68Nb7Ta3Zr4Mo18 (at.%) high-entropy alloy from the BCC phase to the FCC phase occurs. At high temperatures and low strain rates, grain boundary slip is the main deformation mechanism, and at low temperatures and high strain rates, dislocation slip replaces grain boundary slip as the dominant deformation mechanism, which improves the strength of the alloy. Moreover, when the grain size is too small, the strength of the alloy decreases, which does not satisfy the fine grain strengthening theory and shows an inverse Hall-Petch relationship. This study offers a new compositional window for the additive manufactured lightweight high-strength material categories for various applications including the aerospace industry.
Keywords: dislocation evolution; grain size; high-entropy alloy; molecular dynamics; strain rate.