Multiscale modeling of irradiation-induced defect evolution in BCC multi principal element alloys

Multi-principal element alloys (MPEAs) have garnered significant attention due to their exceptional mechanical properties and resistance to irradiation. The changes in microstructures under irradiation are influenced by the primary damage state and the diffusion and interaction of defects over a prolonged period, presenting a problem that spans several scales. In this work, we present a multiscale modeling of defect evolution in body-centered cubic (BCC) MPEAs by combining molecular dynamics (MD) and cluster dynamics (CD) for the first time, which enables us to link the microscopic scale defect process with the experimentally observable defect structures at a mesoscopic scale and to analyze the critical factors affecting the irradiation performance of MPEAs. In contrary to previous reports on face-centered cubic (FCC) MPEAs, our MD simulations show that the random arrangement of different elements in MPEAs strongly suppresses intra-cascade cluster formation, even compared with their corresponding averaged alloy models (AAM). We then utilize the primary damage states from MD simulations to feed into a CD model and show that cluster growth in random MPEAs is inhibited during the reaction-diffusion stage due to the slower and three-dimensional defect dynamics compared with their corresponding AAMs. Our results elucidate the unique irradiation resistance mechanism of BCC MPEAs and provide essential guidelines for alloy design with controllable defect dynamics.