Short-range ordering alters the dislocation nucleation and propagation in refractory high-entropy alloys

Abstract

<p>The role of short-range ordering (SRO) in the dislocation kinetics in refractory high-entropy alloys (RHEAs) remains controversial. On one hand, it was shown by simulations that the mobility of <a href="https://www.sciencedirect.com/topics/engineering/edge-dislocation" title="Learn more about edge dislocations from ScienceDirect's AI-generated Topic Pages">edge dislocations</a> was enhanced while that of <a href="https://www.sciencedirect.com/topics/engineering/screw-dislocation" title="Learn more about screw dislocations from ScienceDirect's AI-generated Topic Pages">screw dislocations</a> was reduced, leading to the conclusion that <a href="https://www.sciencedirect.com/topics/engineering/screw-dislocation" title="Learn more about screw dislocations from ScienceDirect's AI-generated Topic Pages">screw dislocations</a> should be dominant. On the other hand, experiments exclusively showed the dominance of <a href="https://www.sciencedirect.com/topics/engineering/edge-dislocation" title="Learn more about edge dislocations from ScienceDirect's AI-generated Topic Pages">edge dislocations</a>. Here, we investigate the impact of SRO in the grain interior and grain boundary on dislocation nucleation and propagation in a <a href="https://www.sciencedirect.com/topics/engineering/body-centered-cubic" title="Learn more about BCC from ScienceDirect's AI-generated Topic Pages">BCC</a> MoTaTiWZr RHEA, using a combination of the density-functional theory calculations, <a href="https://www.sciencedirect.com/topics/chemistry/monte-carlo-method" title="Learn more about Monte Carlo method from ScienceDirect's AI-generated Topic Pages">Monte Carlo method</a>, and <a href="https://www.sciencedirect.com/topics/chemistry/molecular-dynamics" title="Learn more about molecular dynamic simulation from ScienceDirect's AI-generated Topic Pages">molecular dynamic simulation</a>. Our results show that this RHEA is energetically favorable to undergo SRO, thus forming a pseudo-composite microstructure. This microstructure consists of three categories of clusters: high energy clusters (HECs), medium energy clusters (MECs), and low energy clusters (LECs), with the HECs in grain boundaries acting as weak fillers to induce dislocation nucleation while the MECs/LECs serving as a strong matrix to stabilize the weak HECs. Importantly, SRO is found to enhance the energy barriers for both edge and screw dislocation motion and make the mobility of edge dislocations comparable to or even lower than screw dislocations, contributing to the dominance of edge dislocations in the <a href="https://www.sciencedirect.com/topics/engineering/body-centered-cubic" title="Learn more about BCC from ScienceDirect's AI-generated Topic Pages">BCC</a> RHEA. Our work highlights the importance of SRO in influencing the dislocation activity of RHEAs and presents a fascinating route for designing RHEAs to achieve superior <a href="https://www.sciencedirect.com/topics/materials-science/mechanical-property" title="Learn more about mechanical properties from ScienceDirect's AI-generated Topic Pages">mechanical properties</a>.</p>