Effect of elemental combination on friction stress and Hall-Petch relationship in face-centered cubic high / medium entropy alloys
Effect of elemental combination on friction stress and Hall-Petch relationship in face-centered cubic high / medium entropy alloys
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DOI：
10.1016/j.actamat.2019.04.017
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发表时间：
2019-06
期刊：
影响因子：
9.4
通讯作者：
S. Yoshida;T. Ikeuchi;T. Bhattacharjee;Y. Bai;A. Shibata;N. Tsuji
中科院分区：
文献类型：
--
作者：
S. Yoshida;T. Ikeuchi;T. Bhattacharjee;Y. Bai;A. Shibata;N. Tsuji
在这项研究中，我们报告的元素组合的摩擦应力和Hall-Petch关系的中熵合金（MEA）和高熵合金（HEAs），定义为合金组成的四个或更少和五个或更多的主要元素，分别与（近）等原子浓度。多边环境协定（CoCrFeNi、CoCrNi等），的等原子的CoCrFeMnNi HEA的子系统，通过高压扭转（HPT）高度变形，随后在不同的温度下退火。获得了具有面心立方单相完全再结晶组织的试样，其平均晶粒尺寸可达亚微米级。随后，在室温下进行拉伸试验，以获得精确的Hall-Petch关系和材料的摩擦应力。采用修正的Labusch固溶强化模型（即平均场Labusch模型）成功预测了Co20（CrNi）80合金的强度。摩擦应力的实验值被发现非常符合模型，表明合金的强度是密切相关的完全扭曲的晶格作为高密度障碍位错运动的合金。与此同时，发现合金中的平均晶格畸变值与一些稀释合金中的值相当，尽管“严重”晶格畸变被认为是比稀释系统更高强度的原因。最后，提出了一种元素-元素相互作用的强化机制，作为提高FCC HEAs和MEA强度的附加机制。
In this study, we report the effect of elemental combinations on the friction stress and Hall-Petch relationship in medium entropy alloys (MEAs) and high entropy alloys (HEAs) which are defined as the alloys composed of four or less and five or more principal elements, respectively, with (near-) equi-atomic concentrations. The MEAs (CoCrFeNi, CoCrNi, etc.), which are subsystems of equi-atomic CoCrFeMnNi HEA, were highly deformed by high-pressure torsion (HPT) and subsequently annealed at different temperatures. The specimens with fully-recrystallized microstructures of FCC single-phase with various mean grain sizes down to sub-micrometer scale were obtained. Subsequently, tensile tests were performed at room temperature to obtain precise Hall-Petch relationships and friction stresses of the materials. Co20(CrNi)80was successfully predicted as the alloy showing the highest strength among the MEAs by the modified Labusch model (so-called mean field Labusch model) for solution hardening. Experimental values of the friction stresses were found to fit with the model very well, indicating that the strength of the alloys was closely related to entirely distorted crystal lattice acting as high-density obstacles for dislocation motion in the alloys. At the same time, values of the average lattice distortion in the alloys were found comparable to those in some dilute alloys, although “severe” lattice distortion had been believed as a reason for the higher strength than dilute systems. Finally, a strengthening mechanism by element-element interaction was proposed as an additional mechanism to enhance the strength in FCC HEAs and MEAs.