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Transitions in the morphology and critical stresses of gliding dislocations in multiprincipal element alloys

Journal Article · · Physical Review Materials
 [1];  [2];  [3];  [4];  [2]
  1. Univ. of California, Santa Barbara, CA (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Univ. of California, Santa Barbara, CA (United States)
  3. Utah State Univ., Logan, UT (United States)
  4. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Refractory multiprincipal element alloys (MPEAs) are promising material candidates for high-temperature, high-strength applications. However, their deformation mechanisms, particularly at the dislocation scale, are unusual compared to those of conventional alloys, making it challenging to understand the origin of their high strength. Here, using an atomistically informed phase-field dislocation dynamics model, we study transitions in the morphology and critical stresses of long gliding screw dislocations over extended distances in a refractory MPEA. The model MPEA crystal accounts for the atomic-scale fluctuations in chemical composition across the glide planes via spatially correlated lattice energies and for the differences in glide resistances between screw and edge dislocations of unit length. Here, we show that the dislocation moves in a stop-start motion, alternating between wavy morphology in free flight and nearly recovered straight screw orientation in full arrest. The periods of wavy glide are due to variable kink-pair formation and migration rates along the length, where portions with higher rates glide more quickly. The critical stress to initiate motion corresponds to the stress required to form and migrate a kink pair at the weakest region along the length of the dislocation. Heterogeneity in lattice energy leads to variability in the local stress-strain response and to a strain hardening-like response, in which the critical stress to reactivate glide increases with glide distance. Statistical assessment of hundreds of realizations of dislocations indicates that the amount of hardening directly scales with the dispersion in underlying lattice energy.
Research Organization:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Sponsoring Organization:
US Department of the Navy, Office of Naval Research (ONR); USDOE National Nuclear Security Administration (NNSA)
Grant/Contract Number:
89233218CNA000001; NA0003960
OSTI ID:
1865000
Report Number(s):
LA-UR-21-22205
Journal Information:
Physical Review Materials, Journal Name: Physical Review Materials Journal Issue: 1 Vol. 6; ISSN 2475-9953
Publisher:
American Physical Society (APS)Copyright Statement
Country of Publication:
United States
Language:
English

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