Unraveling dual phase transformations in a CrCoNi medium-entropy alloy
Unraveling dual phase transformations in a CrCoNi medium-entropy alloy
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DOI：
10.1016/j.actamat.2021.117112
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发表时间：
2021-06-30
期刊：
影响因子：
9.4
通讯作者：
Xie, Zonghan
中科院分区：
文献类型：
--
作者：
Chen, Yujie;Chen, Dengke;Xie, Zonghan
多主元素合金的出现为高性能金属材料的发展带来了巨大的希望。然而，目前还不清楚MPEAs是否可以提供以前未知的变形机制，以大大提高其机械性能。在这里，我们报告了一种新的变形机制的机械诱导双相变从面心立方（FCC）的六方密堆积（HCP）相，然后回到FCC相与纳米孪晶在CrCoNi中熵合金（MEA）。在相变的两个连续步骤中，沿着< 110 >平行于（0001）（HCP）的不同{111}（FCC）平面，在平行于< 11（2）over bar 0>（HCP）方向的相同（FCC）方向上发生连续剪切，产生高达70%的总剪切转变应变。双相变源于FCC和HCP相中紧密堆积的{111}（FCC）平行于（0001）（HCP）原子层之间的一种独特的容易滑移的能力，导致这些紧密堆积层具有低堆垛层错能的灵活堆垛序列。我们的工作表明，MPEAs可以提供非常规的变形机制，如在CrCoNi MEA的双相变，从而打开机会，提高先进合金的机械性能。(C)2021 Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
The emergence of multi-principal element alloys (MPEAs) holds great promise for the development of high performance metallic materials. However, it remains unclear whether MPEAs can provide previously unknown deformation mechanisms to drastically enhance their mechanical performance. Here we report a new deformation mechanism of mechanically-induced dual phase transformations from the face-centered cubic (FCC) to hexagonal close- packed (HCP) phase and then back to the FCC phase with nanotwins in a CrCoNi medium-entropy alloy (MEA). During the two sequential steps of phase transformation, continued shear occurs in the same < 110 >(FCC) parallel to < 11 (2) over bar0 >(HCP) direction along different {111}(FCC) parallel to (0001)(HCP) planes, producing a total shear transformation strain up to 70%. The dual phase transformations stem from a unique capability of facile slip in between the close-packed {111}(FCC) parallel to (0001)(HCP) atomic layers in both FCC and HCP phases, leading to flexible stacking sequences of those close-packed layers with low stacking fault energies. Our work demonstrates that MPEAs can offer unconventional deformation mechanisms such as dual phase transformations in the CrCoNi MEA, thereby opening opportunities for enhancing the mechanical properties of advanced alloys. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.