Critical resolved shear stress for slip and twin nucleation in single crystalline FeNiCoCrMn high entropy alloy
Critical resolved shear stress for slip and twin nucleation in single crystalline FeNiCoCrMn high entropy alloy
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DOI：
10.1016/j.matchar.2017.05.014
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发表时间：
2017-07-01
影响因子：
4.7
通讯作者：
Sehitoglu, Huseyin
中科院分区：
文献类型：
--
作者：
Abuzaid, Wael;Sehitoglu, Huseyin
高熵合金是一类新兴的材料，具有优异的机械性能，直至低温。据报道，在77 K时，与传统金属合金不同，其强度、应变硬化率和延展性都有所提高。这种性能的增强归因于在低变形温度下孪生的激活作为一种额外的变形机制。孪晶的形成趋势和晶体取向对硬化响应的依赖性尚未得到充分的研究。本研究旨在探讨等原子FeNiCoCrMn高熵合金在室温（RT）和77 K下不同晶向的变形演化。该工作旨在建立滑移和孪晶的临界分解剪应力（CRSS），并研究这些量级的取向和温度依赖性。实验结果表明，滑移的CRSS具有很强的温度依赖性，从室温下的56 MPa增加到77 K时的153 MPa，而取向依赖性可以忽略不计。在77 K时，即使在高变形水平下，也不是所有的晶体取向都发展成孪晶。正如本研究所确定的那样，缺乏孪晶是由于硬化响应的差异导致的低应力水平低于153mpa的孪晶CRSS。在室温下，无论硬化程度和获得的应力如何，在任何变形的晶体取向上都没有观察到孪生。综上所述，本工作的结果增强了我们对单晶FeNiCoCrMn高熵合金的局部变形响应的理解，特别是滑移的形核、孪生的形核，以及晶体取向和加载温度对这些变形机制的影响。
High entropy alloys is an emerging class of materials with superior mechanical properties down to cryogenic temperatures. At 77 K, and unlike traditional metallic alloys, an increase in strength, strain hardening rate, and ductility has been reported. This enhancement in properties has been attributed to the activation of twinning as an additional deformation mechanism at low deformation temperatures. The tendency for the formation of twinning and the hardening response dependence on crystal orientation has not been fully explored. This study is dedicated to explore the deformation evolution across several crystal orientations for the equiatomic FeNiCoCrMn high entropy alloy at room temperature (RT) and 77 K. The works aims to establish the critical resolved shear stresses (CRSS) for slip and twinning and study the orientation and temperature dependence in these magnitudes. The experimental results have revealed a strong temperature dependence in the CRSS for slip, increasing from 56 MPa at RT to 153 MPa at 77 K, with negligible orientation dependence. At 77 K, not all crystal orientations developed twinning even at high levels of deformation. The lack of twinning has been attributed to differences in the hardening response resulting in low stress levels below the twinning CRSS of 153 MPa, as established in this work. No twinning was observed in any of the crystal orientations deformed at room temperature, regardless of the level of hardening and the achieved stresses. Overall, the results discussed in this work enhances our understanding of the local deformation response in single crystalline FeNiCoCrMn high entropy alloy, particularly the nucleation of slip, nucleation of twinning, and the effect of crystal orientation and loading temperature on these deformation mechanisms.