Multiplicity of dislocation pathways in a refractory multiprincipal element alloy

Pathways for ductility

Alloys containing multiple elements can be very strong but often suffer from poor ductility. F. Wang et al. found that different mechanisms accommodated plasticity in a molybdenum-niobium-titanium multiprincipal element alloy (see the Perspective by Cairney). Instead of so-called “screw” dislocations, deformation is accommodated by multiple pathways that include “edge” dislocations and activation of crystallographic slip planes. These results offer a design paradigm for developing new high-strength alloys.

Science, this issue p. 95; see also p. 37


Refractory multiprincipal element alloys (MPEAs) are promising materials to meet the demands of aggressive structural applications, yet require fundamentally different avenues for accommodating plastic deformation in the body-centered cubic (bcc) variants of these alloys. We show a desirable combination of homogeneous plastic deformability and strength in the bcc MPEA MoNbTi, enabled by the rugged atomic environment through which dislocations must navigate. Our observations of dislocation motion and atomistic calculations unveil the unexpected dominance of nonscrew character dislocations and numerous slip planes for dislocation glide. This behavior lends credence to theories that explain the exceptional high temperature strength of similar alloys. Our results advance a defect-aware perspective to alloy design strategies for materials capable of performance across the temperature spectrum.

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