Regulation of stacking fault energy and manipulation of mechanical mechanism for developing novel superior high entropy alloys

2020 Fiscal Year Final Research Report

• Project/Area Number: 19K14838
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 18010:Mechanics of materials and materials-related
• Research Institution: Tohoku University
• Principal Investigator: Wei Daixiu 東北大学, 金属材料研究所, 助教 (20785810)
• Project Period (FY): 2019-04-01 – 2021-03-31
• Keywords: 金属材料 / 機械特性 / 第一原理計算 / 熱力学計算 / 塑性変形 / 強度 / 延性

Outline of Final Research Achievements

High-entropy alloys (HEAs) have attracted much attention, with stacking fault energy (SFE) affecting their mechanical behaviors. The present study revealed the principles for regulating elastic and plastic behaviors of the quaternary CoCrFeNi and quinary CoCrFeMnNi HEAs, assisted by ab initio and thermodynamics calculations. The results showed that an increase in Co content and a decrease in Fe and Ni contents reduced the SFE, but enhanced the elastic modulus, anisotropy, and lattice friction stress. Minor addition of Mo increased the lattice distortion but decreased the SFE and elastic modulus. Then, a series of strong and ductile metastable Co-rich HEAs with superior mechanical properties were proposed. The properties are enhanced by solid-solution strengthening accompanied by a low-SFE-induced restriction of planar behavior of dislocations, mechanical twinning, and strain-induced martensitic transformation. The findings shed light on the development of high-performance HEAs.

Free Research Field

材料加工

Academic Significance and Societal Importance of the Research Achievements

金属材料が工業的に用いられる材料の中でも重要な地位を占めているが、一般に金属材料を高強度化すると、その一方で延性が低下する。そこで研究者は高強度および高延性を両立させる金属材料の開発を目指している。ハイエントロピー合金には、従来合金には見られない特異で優れた機械的特性を示すものが多く見られます。本研究は、第一原理計算、熱力学計算と実験を融合することで、ハイエントロピー合金の開発および力学特性を向上する指針を明らかにした。積層欠陥エネルギーの低下と格子歪みの増加により、高強度と高延性の両立を可能にした。今後の次世代高性能金属材料開発設計に大きく寄与するものであると考える。