Portevin-Le Chatelier mechanism in face-centered-cubic metallic alloys from low to high entropy

• Published in: International journal of plasticity Vol. 122; no. C; pp. 212 - 224
• Main Authors: Tsai, Che-Wei, Lee, Chi, Lin, Po-Ting, Xie, Xie, Chen, Shuying, Carroll, Robert, LeBlanc, Michael, Brinkman, Braden A.W., Liaw, Peter K., Dahmen, Karin A., Yeh, Jien-Wei
• Format: Journal Article
• Language: English
• Published: New York Elsevier Ltd 01.11.2019; Elsevier BV; Elsevier
• Subjects: Diffusion; Dislocation pinning; Face centered cubic lattice; High entropy alloys; High-entropy alloy; Medium-entropy alloy; Nickel; Portevin-Le Chatelier effect; Room temperature; Serration mechanism; Solutes; Strain rate; Stress-strain curves; Substitutional alloy; Tensile tests; Serration mechanism; Substitutional alloy; Portevin-Le Chatelier effect; Medium-entropy alloy; High-entropy alloy
• ISSN: 0749-6419; 1879-2154
• DOI: 10.1016/j.ijplas.2019.07.003

Serration phenomena during tensile testing on certain alloys with diffusing solute atoms (i.e., Portevin–Le Chatelier effect) have been observed for a long time, but detailed mechanisms are not fully clear yet. This study is intended to find the mechanism from different approaches verified by tensile testing on a series of single-phase face-centered-cubic (FCC) pure metal and alloys: Ni, CoNi, CoFeNi, CoCrFeNi, and CoCrFeMnNi, which range from low to high configurational entropy. The results of tensile tests, at strain rates from 1 × 10−5 to 1 × 10−2/s and temperature from room temperature to 700 °C, show that serrations occur on stress-strain curves of CoFeNi, CoCrFeNi, and CoCrFeMnNi alloys in their specific temperature and strain-rate regime. A mechanism for dislocation pinning is proposed and verified with theoretical calculation for the present substitutional alloys. The proposed mechanism involves the in-situ rearrangement of substitutional solute atoms by “local dislocation-core diffusion” and might also be applied to similar substitutional alloys. [Display omitted] •PLC effect and its trend are identified in Ni, CoNi, CoFeNi, CoFeNiCr, and CoCrFeMnNi alloys from low to high entropy.•Actual mechanism of PLC effect relating with in-situ dislocation pinning by dislocation-core diffusion is proved.•The mechanism could be generalized to substitutional solid solution alloys.