Thermal activation parameters of plastic flow reveal deformation mechanisms in the CrMnFeCoNi high-entropy alloy
Thermal activation parameters of plastic flow reveal deformation mechanisms in the CrMnFeCoNi high-entropy alloy
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DOI：
10.1016/j.actamat.2017.10.014
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发表时间：
2018-01-15
期刊：
影响因子：
9.4
通讯作者：
George, E. P.
中科院分区：
文献类型：
--
作者：
Laplanche, G.;Bonneville, J.;George, E. P.
为了揭示面心立方高熵合金的塑性变形机制，通过反复载荷松弛实验，测量了CrMnFeCoNi合金在77~423K范围内的激活体积随塑性应变和温度的变化关系。在屈服应力Sigma(Y)下，激活体积从77K时的60b(3)变化到293K时的360b(3)，并与屈服应力成反比。随着塑性应变的增加，激活体积减小，变化趋势符合Cottrell-Stokes定律，根据该定律，激活体积逆应该与sigma-sigma(Y)线性增加(Haasen图)。这与以下观点是一致的，即由于位错密度的增加而导致的硬化与激活体积的减少自然相关，因为位错之间的间距减小。活化体积的数值和趋势与将HEA视为高浓度固溶强化合金的理论预测一致。这些结果表明，这种HEA是通过面心立方合金中典型的溶质强化机制来变形的，从而表明高的成分/结构复杂性并没有引入任何新的本征变形机制。(C)2017 Acta Materialia Inc.由Elsevier Ltd.出版。保留所有权利。
To reveal the operating mechanisms of plastic deformation in an FCC high-entropy alloy, the activation volumes in CrMnFeCoNi have been measured as a function of plastic strain and temperature between 77 K and 423 K using repeated load relaxation experiments. At the yield stress, sigma(y), the activation volume varies from similar to 60 b(3) at 77 K to similar to 360 b(3) at 293 K and scales inversely with yield stress. With increasing plastic strain, the activation volume decreases and the trends follow the Cottrell-Stokes law, according to which the inverse activation volume should increase linearly with sigma - sigma(y) (Haasen plot). This is consistent with the notion that hardening due to an increase in the density of forest dislocations is naturally associated with a decrease in the activation volume because the spacing between dislocations decreases. The values and trends in activation volume agree with theoretical predictions that treat the HEA as a high-concentration solid-solution-strengthened alloy. These results demonstrate that this HEA deforms by the mechanisms typical of solute strengthening in FCC alloys, and thus indicate that the high compositional/structural complexity does not introduce any new intrinsic deformation mechanisms. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.