Orientation dependent plasticity of the refractory multi-principal element alloy MoNbTi investigated via micropillar compression

Refractory multi-principal element alloys (RMPEAs) are promising candidate materials for use in high temperature structural applications and other extreme environments. Recent experiments and simulations have highlighted the unusual deformation behavior of an equiatomic MoNbTi alloy, which exhibits slip on higher order planes and sluggish edge dislocation mobility. In this work, we utilize micropillar compression and postmortem transmission electron microscopy to elucidate the orientation dependent deformation behavior of MoNbTi. Our results suggest that deformation in this system is largely mediated by kink-migration of screw dislocations, as evidenced by the presence of long screw dislocations and significant dislocation debris in postmortem observations, and the absence of twinning/anti-twinning asymmetry. Moreover, we report an unusual orientation dependence of the yield strength, owing to the high stress required to facilitate slip on {110} type planes. These results further demonstrate the unconventional plasticity in BCC RMPEAs, and provide experimental verification that kink-migration is the rate limiting feature in this alloy at low temperatures.

Automated summary

Refractory multi-principal element alloys (RMPEAs) have great potential for high temperature structural applications and other extreme environments. Recent experiments and simulations have revealed the unusual deformation behavior of equiatomic MoNbTi alloy, which shows slip on higher order planes and slow movement of edge dislocations. In this study, micropillar compression and postmortem transmission electron microscopy were used to investigate the orientation-dependent deformation behavior of MoNbTi. The results indicate that kink-migration of screw dislocations is the dominant mechanism for deformation in this system. Additionally, an unusual orientation dependence of yield strength was observed, which can be attributed to the high stress required for slip on {110} type planes.