具有优异微力学性能的纳米层状高熵合金
Nanolamellar Hybrid High-Entropy Alloys with Superior Micromechanical Properties
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中文总结 AI 辅助
本研究结合两种高熵合金，通过高压扭转制备出层厚约61 nm的BCC/FCC纳米层状混合结构，其强度、硬度优异且保留一定延展性，源于晶界强化、缺陷及相界强化的协同作用。
中文摘要 AI 辅助
珠光体钢等具有纳米层状结构的金属材料兼具高强度与合适的延展性。鉴于这类纳米层状结构有望打破金属合金传统的强度-延展性权衡关系，本研究旨在通过结合两种不同的高熵合金（HEA），开发出具有优异微力学性能的独特纳米层状结构。将具有面心立方（FCC）结构的Al0.1CoCrFeNi合金与具有体心立方（BCC）结构的TiZrHfNbTa合金，通过对每种合金的半圆盘进行高压扭转（HPT）工艺实现结合，最终形成层状混合结构，其层厚度低至约61 nm。该BCC/FCC纳米层状混合结构展现出优异的性能组合：极限抗拉强度达2.4 GPa，最大弯曲强度达4.0 GPa，硬度达740 Hv，同时在拉伸和弯曲载荷下仍保留一定的延展性/塑性。通过同步辐射衍射、电子显微镜和原子探针断层扫描的详细分析表明，其强度和硬度优于纳米结构HEA，源于三个因素：（i）平均尺寸为22 nm的纳米晶粒带来的极致晶界强化；（ii）缺陷的存在，包括FCC和BCC中的位错、FCC中的堆垛层错以及FCC中的孪晶；（iii）BCC/FCC纳米层状界面带来的相界强化，对总硬度的贡献约为30%。本研究证明，通过HPT将两种HEA结合成富含缺陷的混合纳米层状复合材料，可形成超高强度与合理延展性/塑性的有潜力协同效应。
英文摘要
Metallic materials with nanolamellar structures, such as pearlitic steels, exhibit high strength with appropriate ductility. Considering the potential ability of such nanolamellar structures to break the traditional strength-ductility trade-off in metallic alloys, this study aims at developing a unique nanolamellar structure with superior micromechanical properties by combining two different high-entropy alloys (HEAs). Al0.1CoCrFeNi with the face-centered cubic (FCC) structure is combined with TiZrHfNbTa with the body-centered cubic (BCC) structure using high-pressure torsion (HPT) of half discs of each alloy. That way, a layered hybrid structure was formed, with layer thickness down to about 61 nm. The BCC/FCC nanolamellar hybrid structure exhibits an exceptional combination of properties with an ultimate tensile strength of 2.4 GPa, a maximum bending strength of 4.0 GPa, and a hardness of 740 Hv, while retaining some ductility/plasticity under both tensile and bending loads. Detailed analyses by synchrotron diffraction, electron microscopy and atom probe tomography suggests that these high strength and hardness, which are superior to those of nanostructured HEAs, result from: (i) extreme grain boundary strengthening from nanograins with a mean size of 22 nm, (ii) presence of defects such as dislocations in FCC and BCC, stacking faults in FCC and twins in FCC, and (iii) interphase hardening from BCC/FCC nanolamellar boundaries with about 30% contribution to the total hardness. This work demonstrates that combining two HEAs using HPT into a defect-rich hybrid nanolamellar composite forms a promising synergy of ultrahigh strength and reasonable ductility/plasticity.
