Orientation dependence of the effect of short-range ordering on the plastic deformation of a medium entropy alloy

Sezer Picak, Prashant Singh, D Salas, X Fang, Matheus Tunes, L. Zhou, Matthew Joseph Kramer, Yuriy I. Chumlyakov, Duane D. Johnson, Raymundo Arróyave, Y. Ren, I. Karaman

Research output: Contribution to journalArticleResearchpeer-review


Multi-principal-element alloys (also known as medium and high entropy alloys) offer a much larger and richer design space than conventional alloys, providing opportunities for discovering new functionalities and their governing physics. Some of these alloys exhibit an outstanding combination of high strength and ductility, linked to the activation of various deformation modes triggered by low-energy stacking faults. However, a pressing question remains: Is the plasticity of medium- and high-entropy alloys governed only by stacking fault energy, or does atomic short-range order (SRO) play a role? To answer this, we investigated how SRO affects the deformation in single-crystalline NiCoCr, with previous contradictory findings. First, we established unique experimental evidence for SRO formation in bulk single crystals using high-energy synchrotron transmission X-Ray Diffraction. By tuning the degree of SRO by aging at high temperatures, twinning density and strain-induced martensitic phase transformation can be significantly increased in the [110] and [111] orientations under tension, increasing the tensile ductility; yet, no increase was observed along the [001] orientation due to lack of TWinning-Induced Plasticity (TWIP) or TRansformation-Induced Plasticity (TRIP), indicating a strong crystallographic orientation dependence. Our first-principles thermodynamic calculations unequivocally show SRO exists and governs the observed microstructural evolution and deformation hardening behavior. Here we find direct proof that SRO triggers a simultaneous TWIP and TRIP in NiCoCr, a rare microstructural evolution path. Our findings establish that the interplay of SRO and plasticity could be exploited to alter deformation modes and yield unprecedented mechanical response in medium- and high-entropy alloys.
Original languageEnglish
Article number145309
Number of pages11
JournalMaterials Science and Engineering: A
Issue number17 November
Publication statusE-pub ahead of print - 22 Jun 2023
Externally publishedYes

Bibliographical note

Publisher Copyright: © 2023 Elsevier B.V.

Cite this