Mechanical behaviors of equiatomic and near-equiatomic face-centered-cubic phase high-entropy alloys probed using in situ neutron diffraction
Mechanical behaviors of equiatomic and near-equiatomic face-centered-cubic phase high-entropy alloys probed using in situ neutron diffraction
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DOI：
10.1016/j.ijplas.2022.103417
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发表时间：
2022-09
影响因子：
9.8
通讯作者：
Daixiu Wei;W. Gong;T. Tsuru;T. Kawasaki;S. Harjo;B. Cai;P. Liaw;Hidemi Kato
中科院分区：
文献类型：
--
作者：
Daixiu Wei;W. Gong;T. Tsuru;T. Kawasaki;S. Harjo;B. Cai;P. Liaw;Hidemi Kato
等原子CoCrFeMnNi Cantor合金是一种面心立方（FCC）单相高熵合金（HEA），因其高强度和宽温度范围内的良好延展性而备受关注。通过对合金成分进行改性，降低了层错能（SFE），从而提高了合金的力学性能，从而开发出了一系列比其前任更强、更有韧性的近原子或非等原子HEAs。然而，塑性变形行为和强化机制尚未完全发现。在本研究中，我们用情景中子衍射结合第一性原理法和电镜表征研究了不同sfe的康托合金和fcc相富co - HEAs的屈服和硬化行为。富co HEAs具有比Cantor合金更高的固有屈服强度，主要原因是其剪切模量或模量失配更大，晶粒细化在提高低sfe HEAs屈服强度方面更为有效。此外，在拉伸变形过程中，较高的位错密度和较多的层错使富co HEAs具有较高的流变应力和较好的塑性，从而提高了应变硬化速率。低SFE促进了机械孪晶，马氏体相变促进了较高的应变硬化速率。本研究为fcc相HEAs的屈服和硬化提供了深入的见解，对其的理解是开发高性能材料的先决条件。
The equiatomic CoCrFeMnNi Cantor alloy, a face-centered-cubic (FCC) single-phase high-entropy alloy (HEA), has attracted considerable attention owing to its high strength and good ductility over a wide temperature range. The mechanical performance of this alloy was improved by reducing the stacking fault energy (SFE) through composition modification, and thus, a series of near- or non-equiatomic HEAs that are stronger and more ductile than their predecessor have been developed. However, the plastic-deformation behavior and strengthening mechanisms have not yet been fully discovered. In this study, we investigated the yielding and hardening behaviors of the Cantor alloy and FCC-phase Co-rich HEAs with different SFEs byin situneutron diffraction combined with the first-principles method and electron-microscopy characterizations. The Co-rich HEAs exhibited a higher intrinsic yield strength than the Cantor alloy, mainly because of the larger shear modulus or modulus misfit, and grain refinement being more effective in improving the yield strength of low-SFE HEAs. Furthermore, higher flow stresses and better ductility of the Co-rich HEAs are attributed to the greater dislocation density and a larger number of stacking faults, which enhanced the strain-hardening rate during tensile deformation. The low SFE promoted mechanical twinning, and martensitic transformation contributed to higher strain-hardening rates. The present study provides deep insight into the yielding and hardening of FCC-phase HEAs, the understanding of which is a prerequisite for developing high-performance materials.