Molecular dynamics simulation of tensile mechanical properties of AlxCoCrFeNi
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摘要: 采用分子动力学方法研究了AlxCoCrFeNi高熵合金（HEAs）在单轴拉伸下的微观组织演变、变形机制和力学性能，重点研究了Al摩尔比0.1至1.0时Al含量、高温和高应变速率对AlxCoCrFeNi力学性能的影响。研究表明：Al摩尔比0.1至1.0时，常温环境下（300 K）屈服应力及应变随Al含量及温度的上升呈下降趋势。Al含量的增加导致HEAs会在更小的应变处开始屈服，更早进入屈服阶段，从而使HEAs更容易变形，力学性能降低。在300～1500 K环境下随着温度的上升，位错逐渐减少，不同位错之间的相互作用减弱，无法形成固定位错阻碍材料运动，导致材料强度下降。AlxCoCrFeNi屈服应变、应力与应变速率变化呈正相关，且屈服应力对高应变速率敏感。Abstract: In this paper, the molecular dynamics method studied the microstructural evolution, deformation mechanism, and mechanical properties of AlxCoCrFeNi high entropy alloy (HEAs) under uniaxial tension. The effects of Al content, high temperature, and high strain rate on the mechanical properties of AlxCoCrFeNi at 0.1 to 1.0 molar ratio were investigated. The results show that when the molar ratio of Al is 0.1 to 1.0, the yield strain and stress at room temperature (300 K) decrease with the Al content and temperature increase. With the increase of Al content, HEAS will begin to yield at a minor strain and enter the yield stage earlier, which makes HEAS easier to deform and reduce the mechanical properties. At 300 − 1500 K, with the increase in temperature, the dislocations gradually decrease, the interaction between different dislocations is weakened, and the fixed dislocations cannot be formed, which hinders the movement of materials and leads to the decline of material strength. AlxCoCrFeNi yield strain and yield stress are positively correlated with the change of strain rate, and the yield stress is sensitive to high strain rate.
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Key words:
- high entropy alloy /
- mechanical properties /
- molecular dynamics /
- uniaxial tension /
- temperature
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图 1 Al1.0CoCrFeNi HEAs模型及原子示意
Figure 1. Model and atomic structure of Al1.0CoCrFeNi HEAs
图 2 Al1.0CoCrFeNi拉伸应力-应变曲线
Figure 2. Stress-strain relations of Al1.0CoCrFeNi under tensile loading
图 3 (a)Al1.0CoCrFeNi在单轴拉伸过程中不同应变下的RDF，(b)BCC，HCP，FCC以及Other原子数目随应变的变化
Figure 3. （a）The RDF of Al1.0CoCrFeNi HEA at different strains during uniaxial tension, (b) changes of the numbers of BCC，HCP，FCC and Other atom clusters with strain
图 4 不同拉伸应变下Al1.0CoCrFeNi HEAs的位错演化
Figure 4. Dislocation evolution of Al1.0CoCrFeNi HEAs under different strains
图 5 （a）AlxCoCrFeNi应力-应变曲线，（b）AlxCoCrFeNi屈服应力和杨氏模量曲线，（c）Al0.1CoCrFeNi中FCC，HCP，BCC以及Other原子数目随应变的变化
Figure 5. (a) The stress-strain curve of AlxCoCrFeNi HEAs, (b) The Young’s Modulus and yield stress of AlxCoCrFeNi HEAs as a function of Al concentration, (c) variation of the numbers of FCC, HCP, BCC and Other atom clusters with strain of Al0.1CoCrFeNi
图 6 不同温度下(a) Al1.0CoCrFeNi应力-应变曲线, (b) 屈服应力曲线, (c) 位错总长度变化曲线
Figure 6. (a) The stress-strain curve, (b) the Young’s modulus and the yield stress, (c) variation curve of total dislocation length of Al1.0CoCrFeNi at different temperatures
图 7 不同应变速率下(a) Al1.0CoCrFeNi的应力-应变曲线, (b) 屈服应力曲线, (c) 位错总长度变化曲线
Figure 7. (a) The stress-strain curves，(b) the yield stress, (c) variation curve of total dislocation length of Al1.0CoCrFeNi at different strain rates
表 1 HEAs应变速率及弛豫时间
Table 1. tensile strain rate and relaxation time of HEAs
拉伸应变速率/s−1 弛豫时间/ps 108 5000 5×108 2500 109 500 5×109 250 1010 50 2×1010 25 
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