Anisotropic plasticity mechanisms in a newly synthesised High Entropy Alloy investigated using atomic simulations and nanoindentation experiments
Anisotropic plasticity mechanisms in a newly synthesised High Entropy Alloy investigated using atomic simulations and nanoindentation experiments
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DOI：
10.1016/j.jallcom.2023.172541
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发表时间：
2023-10
影响因子：
6.2
通讯作者：
Pengfei Fan;N. K. Katiyar;Muhammad Arshad;Mingwen Bai;Hui Mao;Saurav Goel
中科院分区：
文献类型：
--
作者：
Pengfei Fan;N. K. Katiyar;Muhammad Arshad;Mingwen Bai;Hui Mao;Saurav Goel
这项工作使用原子模拟和纳米压痕实验，以调查硬度，模量沿亚表面晶体缺陷和位错介导的塑性机制，导致各向异性堆积和局部熵变的高熵合金。实验活动开始于Thermo-Calc相预测的Ni 25 Cu 18.75 Fe 25 Co 25 Al 6.25 HEA，随后使用电弧熔化方法实验合成材料，并在负载控制条件下使用Berkovich压头进行实验纳米压痕。通过MD模拟，一致发现单晶HEA中的h f/h max的值大于0.7，这表明堆积行为占主导地位，而下沉行为不太可能。在（110）和多晶HEA基底的情况下，可以看到压痕滞后回线中的弹性功大于（100）和（111）取向，这解释了（110）取向基底显示出最小的弹性模量和硬度，而（111）单晶HEA显示出最高的弹性模量和硬度。从模拟中可以看出，（110）取向上的“套索”型环和其他取向上的剪切环的交叉，伴随着1/6< 112>（Shockley）、1/2< 110>（完全）、1/3< 001>（Hirth）、1/6< 110>（Stair rod）和1/3< 111>（Frank partials）型位错，表现出竞争塑性事件的早期雪崩。在亚表面中伴随这些位错的缺陷被识别为FCC本征层错（ISF）、相邻的本征层错（四重层错）、共格∑ 3孪晶界和与本征层错相邻的共格孪晶界（三重层错）。EBSD分析表明，（210）取向和< 110>取向族有利于FCC相Ni25Cu18.75Fe25Co25Al6.25HEA的塑性变形。
This work used atomic simulations and nanoindentation experiments to investigate hardness, modulus alongside sub-surface crystal defects and dislocation mediated plasticity mechanisms leading to anisotropic pile up and local entropy variation in high entropy alloys. The experimental campaign began from Thermo-Calc phase prediction of Ni 25 Cu 18.75 Fe 25 Co 25 Al 6.25 HEA which followed experimental synthesis of the material using arc melting method and experimental nanoindentation using a Berkovich indenter under load-controlled conditions. Through MD simulations, the value of h f/h max in monocrystalline HEA was consistently found to be larger than 0.7 which suggested pile-up behaviour to dominate and sink-in behaviour to be unlikely. In the case of (110) and polycrystalline HEA substrates, the elastic work in the indentation hysteresis loop was seen to be larger than the (100) and the (111) orientations which explains that the (110) orientation substrate showed least elastic modulus and hardness while the (111) monocrystalline HEA showed the highest elastic modulus and hardness. From the simulations, a “lasso” type loop on the (110) orientation and cross-over of shear loops on the other orientations accompanied by dislocations of type 1/6< 112>(Shockley), 1/2< 110>(perfect), 1/3< 001>(Hirth), 1/6< 110>(Stair rod) and 1/3< 111>(Frank partials) were seen to manifest an early avalanche of competing plasticity events. The defects accompanying these dislocations in the sub-surface were identified to be FCC intrinsic stacking faults (ISF), adjacent intrinsic stacking faults (quad faults), coherent∑ 3 twin boundary and a coherent twin boundary next to an intrinsic stacking fault (triple fault). The EBSD analysis applied to the MD data showed that the (210) orientation and the< 110> family of directions were seemed to be preferable to plastically deform the FCC phased Ni 25 Cu 18.75 Fe 25 Co 25 Al 6.25 HEA.