Role of Fe/Mn elements tuning in the shock dynamics of CoCrNi-based alloy

Recent researches on concentrated solid solutions have emphasized the role of various solute interactions in determining anomalous dislocation core and plastic deformation. However, the influence path of element tuning under extreme conditions is still unclear. Here, we investigated shock-induced deformation and fracture in CoCrNi-based multi-principal element alloys (MPEAs) tuned by Fe/Mn elements using large-scale molecular dynamics simulations. It was found that Fe/Mn elements could reduce the defect nucleation barrier and improve the plastic deformability. When single-element tuning is applied, the Mn element significantly reduces the production of dislocations, favoring more phase transitions from FCC to BCC or amorphous phase. The results show that Mn significantly reduces the Hugoniot elastic limit (HEL) and spall strength, while the addition of Fe element to CoCrNiMn can alleviate this effect by reducing the degree of lattice distortion. Specially, we analyzed the relationship between void nucleation and shock wave propagation, and explained the single-negative-pressure-zone nucleation as well as complex double-negative-pressure-zone nucleation phenomena. Empirical equations for the spall strength of CoCrNi-based MPEAs adjusted by Fe/Mn elements were established. This work demonstrates a potential strategy for elemental tuning to tailor the mechanical properties of polymorphism in MPEAs.