Probing deformation mechanisms of a FeCoCrNi high-entropy alloy at 293 and 77 K using in situ neutron diffraction
Probing deformation mechanisms of a FeCoCrNi high-entropy alloy at 293 and 77 K using in situ neutron diffraction
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DOI：
10.1016/j.actamat.2018.05.013
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发表时间：
2018-08
期刊：
影响因子：
9.4
通讯作者：
Yiqiang Wang;Bin Liu;K. Yan;Minshi Wang;S. Kabra;Y. Chiu;D. Dye;P. Lee;Yong Liu;B. Cai
中科院分区：
文献类型：
--
作者：
Yiqiang Wang;Bin Liu;K. Yan;Minshi Wang;S. Kabra;Y. Chiu;D. Dye;P. Lee;Yong Liu;B. Cai
用原位中子衍射和相关透射电镜研究了粉末冶金法制备的FeCoNiCr高熵合金在77和293 K下的变形响应。在低温下，合金的强度和塑性得到显著提高。真极限抗拉强度和总延伸率从293 K时的980 MPa增加到45%，在77 K时分别增加到1725 MPa和55%。通过定量的原位中子衍射测量确定了晶格应变、层错几率和位错密度的演化。结果表明，随着变形温度的降低，合金具有更高的形成层错和机械孪晶的倾向，这是由于层错能的降低（在293和77 K时分别估计为32.5 mJ/m2和13 mJ/m2）。通过透射电子显微镜分析证实了低温变形过程中纳米孪晶和孪晶-孪晶相交处体积分数的增加。在低温下的强度和塑性的提高可以归因于位错和纳米孪晶密度的增加。这些发现为高熵合金中孪生诱导塑性的基本控制机制提供了基本的理解，为开发具有优异耐低温环境性能的新合金铺平了道路。
The deformation responses at 77 and 293 K of a FeCoNiCr high-entropy alloy, produced by a powder metallurgy route, are investigated usingin situneutron diffraction and correlative transmission electron microscopy. The strength and ductility of the alloy are significant improved at cryogenic temperatures. The true ultimate tensile strength and total elongation increased from 980 MPa to 45% at 293 K to 1725 MPa and 55% at 77 K, respectively. The evolutions of lattice strain, stacking fault probability, and dislocation density were determined via quantifying thein situneutron diffraction measurements. The results demonstrate that the alloy has a much higher tendency to form stacking faults and mechanical twins as the deformation temperature drops, which is due to the decrease of stacking fault energy (estimated to be 32.5 mJ/m2and 13 mJ/m2at 293 and 77 K, respectively). The increased volume faction of nano-twins and twin-twin intersections, formed during cryogenic temperature deformation, has been confirmed by transmission electron microscopy analysis. The enhanced strength and ductility at cryogenic temperatures can be attributed to the increased density of dislocations and nano-twins. The findings provide a fundamental understanding of underlying governing mechanistic mechanisms for the twinning induced plasticity in high entropy alloys, paving the way for the development of new alloys with superb resistance to cryogenic environments.