Tensile creep mechanisms of laser powder bed fused WE43 alloy with heterogeneous microstructure: Evolution in dislocations and precipitates

• Published in: Journal of materials science & technology Vol. 238; pp. 209 - 229
• Main Authors: Ji, Chen, Li, Kun, Liao, Ruobing, Li, Zice, Yin, Bangzhao, Wen, Peng, Jiang, Bin, Murr, Lawrence E., Pan, Fusheng
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 10.12.2025
• Subjects: Creep; Dislocations; Heterogeneous microstructure; Laser powder bed fusion; Stacking faults; WE43; Laser powder bed fusion; Stacking faults; Creep; Heterogeneous microstructure; WE43; Dislocations
• ISSN: 1005-0302
• DOI: 10.1016/j.jmst.2025.02.063

•The creep mechanisms of laser powder bed fused WE43 alloys with heterogeneous microstructures are systematically elucidated.•Distinct in-situ precipitates strengthen creep resistance through different dislocation-interaction pathways.•Stacking faults arise from coupled solute diffusion and stress-induced shear during creep.•Thermally stable stacking faults effectively impede dislocation motion at elevated temperatures.•In-situ precipitates promote dynamic discontinuous recrystallization, enhancing grain boundary stability at low temperatures yet compromising it under high-temperature conditions. The complex non-equilibrium solidification effects of the laser powder bed fusion (LPBF) combined with the high solubility of rare-earth (RE) elements, provide a new advanced powder metallurgy process for Mg RE alloys with outstanding mechanical performances. However, its creep mechanism has not been revealed yet. The present study systematically investigates and evaluates the high-temperature creep mechanism of LPBFed WE43 alloy under varying temperatures and applied stress conditions. In addition, it thoroughly elucidates the interactions and evolution mechanisms between precipitates and dislocations during the creep process. Subject to residual stresses and thermal cycling, the β phase is formed in the form of “precipitation chains” (PCs) within the grains. The metastable phases β″, β′, and β1 in-situ precipitate between the PCs. The creep resistance of the (LPBFed) WE43 alloy is governed by the evolution of precipitates and their interactions with dislocations during the creep. Under creep conditions at 200 °C, a large number of 〈c + a〉 and 〈a〉 dislocations undergo climb and cross-slip behaviors within the grains. During the climb and cross-slip of dislocations, the Orowan strengthening effect of β″, the cutting mechanisms of β′ and β1 phases relative to dislocations, and the dislocation barriers formed by the β phase arrays collectively impart excellent creep resistance to the WE43 alloy. As creep time progresses, dislocations accumulate within the grains, and the β and β1 phases promote the formation of subgrain boundaries, further triggering discontinuous dynamic recrystallization behaviors during the creep process. Furthermore, influenced by the directional diffusion of elements, precipitates dynamically form around the grain boundaries of recrystallized grains, thereby enhancing the resistance to grain boundary sliding. When the creep temperature increases to 250 °C or 300 °C, a large number of 〈c + a〉 dislocations, accompanied by the dissolution of metastable phases and elemental re-diffusion, transform during the creep process into stacking faults (SFs). SFs not only exhibit high thermal stability but also act as effective dislocation barriers at high temperatures through lattice mismatch mechanisms. However, under high-temperature conditions, thermal activation leads to the dissolution of unstable metastable phases, promoting rapid coarsening and transformation of precipitates into various morphologies of β phases, thereby causing a catastrophic decline in creep performance. At the same time, high temperatures further exacerbate elemental diffusion, resulting in precipitate-free zones near grain boundaries, thereby inducing crack initiation. Therefore, the creep resistance of as-deposited alloys decreases significantly at higher temperatures. Building on this, the future development trends of LPBFed WE43 alloys are envisioned, where homogenizing heterostructures or introducing high aspect ratio precipitates and high-density SFs prior to creep can be regarded as a promising approach for enhancing creep resistance in LPBFed WE43 alloys. [Display omitted]