Coupling effects of temperature and strain rate on the mechanical behavior and microstructure evolution of a powder-plasma-arc additive manufactured high-entropy alloy with multi-heterogeneous microstructures

A single-phase or simple-structured alloy does not always possess outstanding combinations of strength and ductility over a wide range of temperatures and strain rates for engineering applications. In the present work, a high-entropy alloy with multi-heterogeneous microstructures was in-situ fabricated via powder-plasma-arc additive manufacturing. The compressive behavior of the additive manufactured high-entropy alloy over a wide range of temperatures and strain rates was studied, using an improved split Hopkinson bar system and electronic universal testing machine. It shows exceptional combination of strength and ductility within the selected temperature and strain rate ranges. Microstructural evolution was characterized at various temperatures and strain rates, providing insight into the intricate relationship between microstructure and property. The multicomponent Laves phase is hard yet deformable, while the multicomponent FCC phase is soft and ductile. The deformation twins observed all over the selected temperature and strain rate ranges and dynamic recrystallization appearing at high temperatures in the FCC phase enhance the ductility of the FCC phase and rise the crack-arresting capability. The third-type strain aging occurs at different strain rates, which shifts to a higher temperature range as strain rate increases. Ta and impurity atom, Si, acting as "solute atoms" form atom atmosphere and silicide, pinning the moving dislocations in the FCC phase. Finally, a deformation mechanism map was proposed over a wide temperature and strain rate range. The study explored a potentially new avenue to design alloys with exceptional combinations of strength and ductility over a wide range of temperatures and strain rates.