Atomistic simulations of dislocation mobility in refractory high-entropy alloys and the effect of chemical short-range order

Sheng Yin,Anas Abu-Odeh,Robert O Ritchie,Xiang-Guo Li,Hui Zheng,Jun Ding,Mark Asta,Shyue Ping Ong,Yunxing Zuo

doi:10.1038/s41467-021-25134-0

Abstract

Refractory high-entropy alloys (RHEAs) are designed for high elevated-temperature strength, with both edge and screw dislocations playing an important role for plastic deformation. However, they can also display a significant energetic driving force for chemical short-range ordering (SRO). Here, we investigate mechanisms underlying the mobilities of screw and edge dislocations in the body-centered cubic MoNbTaW RHEA over a wide temperature range using extensive molecular dynamics simulations based on a highly-accurate machine-learning interatomic potential. Further, we specifically evaluate how these mechanisms are affected by the presence of SRO. The mobility of edge dislocations is found to be enhanced by the presence of SRO, whereas the rate of double-kink nucleation in the motion of screw dislocations is reduced, although this influence of SRO appears to be attenuated at increasing temperature. Independent of the presence of SRO, a cross-slip locking mechanism is observed for the motion of screws, which provides for extra strengthening for refractory high-entropy alloy system.

Highlights

Refractory high-entropy alloys (RHEAs) are designed for high elevated-temperature strength, with both edge and screw dislocations playing an important role for plastic deformation
Using training data reported previously[24] for elemental, binary, ternary, and quaternary systems in Nb–Ta–Mo–W, we developed a potential for the MoNbTaW RHEA based on the moment tensor potential (MTP) formalism, which has been found to feature an excellent balance between accuracy and computational cost[46]
While the mean absolute errors (MAEs) of energies of 4.6 and 4.3 meV atom−1 for respective training and test data are similar to those reported for previously developed potentials[24], the MAEs of forces were decreased by half using the present implementation of MTP, compared to the previous spectral neighbor analysis potential (SNAP)[24]

Summary

Introduction

Refractory high-entropy alloys (RHEAs) are designed for high elevated-temperature strength, with both edge and screw dislocations playing an important role for plastic deformation. We have fit screw dislocation velocity data, in the absence of the cross-kink pinning, in the MoNbTaW RHEA with a phenomenological model that includes the effect of SRO on the formation energy for a double kink.

Results

Conclusion