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Analysis of damage-tolerance of TRIP-assisted V10Cr10Fe45Co30Ni5 high-entropy alloy at room and cryogenic temperatures
Journal of Alloys and Compounds ( IF 6.2 ) Pub Date : 2020-12-01 , DOI: 10.1016/j.jallcom.2020.156090
Yong Hee Jo , Junha Yang , Kyung-Yeon Doh , Woojin An , Dae Woong Kim , Hyokyung Sung , Donghwa Lee , Hyoung Seop Kim , Seok Su Sohn , Sunghak Lee

Abstract A single-phase face-centered-cubic (FCC) high- or medium-entropy alloys (HEAs or MEAs) have attracted great attentions due to their novel damage-tolerance properties (strength, ductility, and fracture toughness) by generating nano-twins at cryogenic temperature. The fracture toughness assessment is essential for evaluating the reliability of high-performance materials for cryogenic applications; however, fracture studies on single-phase FCC HEAs showing transformation-induced plasticity (TRIP) have been hardly conducted. In this study, thus, damage-tolerance mechanisms of a V10Cr10Fe45Co30Ni5 HEA showing the FCC to body-centered-cubic (BCC) TRIP were investigated at room and cryogenic temperatures. At room temperature (298 K), the alloy shows the tensile strength of 731 MPa, elongation of 40%, and fracture toughness (KJIc) of 230 MPa m1/2. At cryogenic temperature (77 K), the strength and elongation improve to 1.2 GPa and 66%, respectively, while the KJIc remains almost constant at 237 MPa m1/2. Dislocation-mediated plasticity prevails at 298 K; however, the TRIP from FCC to BCC occurs at 77 K. Deformation and fracture mechanisms are analyzed by stacking fault energies and differences in Gibbs free energies between phases calculated by ab-initio methods, and are compared to those of CrMnFeCoNi, CrCoNi, Fe50Mn30Co10Cr10, and V10Cr10Fe45Co20Ni15 alloys. Despite the presence of a considerable amount of BCC which is intrinsically brittle at low temperature, the transformed BCC martensite shows ductile fracture after the fracture toughness test even in cryogenic environments. These results demonstrate that the FCC to BCC TRIP can be an attractive route in a field of HEA design to overcome the strength and toughness trade-off at cryogenic temperature.

中文翻译:

TRIP辅助V10Cr10Fe45Co30Ni5高熵合金常低温损伤容限分析

摘要 单相面心立方 (FCC) 高或中熵合金 (HEA 或 MEA) 通过产生纳米级低温下的双胞胎。断裂韧性评估对于评估用于低温应用的高性能材料的可靠性至关重要;然而,显示相变诱导塑性 (TRIP) 的单相 FCC HEA 的断裂研究几乎没有进行过。因此,在这项研究中,在室温和低温下研究了 V10Cr10Fe45Co30Ni5 HEA 的损伤耐受机制,显示了 FCC 到体心立方 (BCC) TRIP。在室温 (298 K) 下,该合金的抗拉强度为 731 MPa,伸长率为 40%,断裂韧性 (KJIc) 为 230 MPa m1/2。在低温 (77 K) 下,强度和伸长率分别提高到 1.2 GPa 和 66%,而 KJIc 几乎保持不变,为 237 MPa m1/2。位错介导的可塑性在 298 K 时盛行;然而,从 FCC 到 BCC 的 TRIP 发生在 77 K。变形和断裂机制通过堆垛层错能和通过 ab-initio 方法计算的相间吉布斯自由能的差异进行分析,并与 CrMnFeCoNi、CrCoNi、Fe50Mn30Co10Cr10 进行比较,和 V10Cr10Fe45Co20Ni15 合金。尽管存在大量在低温下本质上脆的 BCC,但即使在低温环境下,转变后的 BCC 马氏体在断裂韧性测试后仍显示出韧性断裂。
更新日期:2020-12-01
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