Real-time nanoscale observation of deformation mechanisms in CrCoNi-based medium- to high-entropy alloys at cryogenic temperatures
Real-time nanoscale observation of deformation mechanisms in CrCoNi-based medium- to high-entropy alloys at cryogenic temperatures
复制标题
低温下 CrCoNi 基中高熵合金变形机制的实时纳米尺度观察
DOI：
10.1016/j.mattod.2019.03.001
复制
发表时间：
2019-05-01
期刊：
影响因子：
24.2
通讯作者：
Ritchie, Robert O.
中科院分区：
文献类型：
--
作者：
Ding, Qingqing;Fu, Xiaoqian;Ritchie, Robert O.
工程材料的技术重要的机械性能往往在低温下退化。有一类材料不符合这一趋势，它们是CrCoNi基中熵和高熵合金，因为随着温度的降低，它们显示出更高的强度、延展性和韧性。在这里，我们表明，使用原位应变在透射电子显微镜在93 K（-180摄氏度），其特殊的损伤容限涉及协同作用的变形机制，包括孪生，滑移的部分和完整的位错，广泛的交叉滑移，和多重滑移激活的位错和晶界相互作用。特别是，大量的交叉滑移发生在塑性变形的早期阶段，从而促进多个滑移和位错的相互作用。这些结果表明，在低温下的缺陷的热激活的强度降低和所需的增加施加的应力的连续塑性流动，连同高晶格电阻，在促进多个变形机制的并发操作，这共同使这些合金的出色的机械性能发挥了关键作用。
Technologically important mechanical properties of engineering materials often degrade at low temperatures. One class of materials that defy this trend are CrCoNi-based medium- and high-entropy alloys, as they display enhanced strength, ductility, and toughness with decreasing temperature. Here we show, using in situ straining in the transmission electron microscope at 93 K (-180 degrees C) that their exceptional damage tolerance involves a synergy of deformation mechanisms, including twinning, glide of partials and full dislocations, extensive cross-slip, and multiple slip activated by dislocation and grain-boundary interactions. In particular, massive cross-slip occurs at the early stages of plastic deformation, thereby promoting multiple slip and dislocation interactions. These results indicate that the reduced intensity of thermal activation of defects at low temperatures and the required increase of applied stress for continued plastic flow, together with high lattice resistance, play a pivotal role in promoting the concurrent operation of multiple deformation mechanisms, which collectively enable the outstanding mechanical properties of these alloys.