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Title: A new route to achieve high strength and high ductility compositions in Cr-Co-Ni-based medium-entropy alloys: A predictive model connecting theoretical calculations and experimental measurements
Authors: Wang, Zhi
Li, Le
Chen, Zhenghao
Yuge, Koretaka  kyouindb  KAKEN_id
Kishida, Kyosuke  kyouindb  KAKEN_id  orcid (unconfirmed)
Inui, Haruyuki
Heilmaier, Martin
Author's alias: 王, 植
李, 楽
陳, 正昊
弓削, 是貴
岸田, 恭輔
乾, 晴行
Keywords: Metals and alloys
Mechanical properties
Dislocations and disclinations
Phase transitions
Computer simulations
Transmission electron microscopy
Issue Date: 10-Oct-2023
Publisher: Elsevier BV
Journal title: Journal of Alloys and Compounds
Volume: 959
Thesis number: 170555
Abstract: A new route to achieve high strength and high ductility compositions in the Cr-Co-Ni medium entropy alloys (MEAs) is proposed, by controlling the solid solution hardening parameter (Mean Square Atomic Displacement, MSAD) and twinning propensity parameter (Stacking Fault Energy, SFE), respectively. The MSAD is calculated to increase with the increase in the Cr content and with the increase in the Ni/Co ratio at high Cr concentrations, while the SFE is calculated to decrease with the increase in the Cr content and with the increase in the Co/Ni ratio at high Cr concentrations. In experiment, the strength at 0 K (derived from the temperature dependence of yield stress) increases as the Cr content increases and/or as the Ni content increases for a given high Cr content, so that a linear correlation is found between the yield strength at 0 K and MSAD. The SFE also decreases as the Cr content increases and as the Co content increases for a given high Cr content. However, while the tensile elongation increases with the decrease in SFE down to SFE values of 10–12 mJ/m2, it abruptly decreases once the SFE decreases below this value due to a change in major deformation mode from deformation twinning to deformation-induced ε-martensite transformation. Based on the established connection between the theoretical calculation and experimental measurement, outstanding combinations of strength and ductility are predicted and experimentally confirmed at high Cr compositions and at a bit Ni-rich side of the Co/Ni equi-composition line. The proposed composition (around 45Cr-20Co-35Ni) exhibits a greater 0 K strength and a superior 77 K tensile ductility by 32 % and 13 %, respectively, compared to those of the equiatomic Cr-Co-Ni alloy.
Description: 新規高強度高延性合金の開発に成功 --計算と実験の融合による合金設計法の確立--. 京都大学プレスリリース. 2023-05-25.
Rights: © 2023 The Authors. Published by Elsevier B.V.
This is an open access article under the CC BY license.
DOI(Published Version): 10.1016/j.jallcom.2023.170555
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