CoCrFeNiAl<sub><i>x</i></sub>系高熵合金的动态力学性能和本构关系

马胜国; 王志华

doi:10.11883/bzycj-2020-0293

CoCrFeNiAl_x系高熵合金的动态力学性能和本构关系

doi: 10.11883/bzycj-2020-0293

马胜国^{1, 2, 3,},
王志华^{1, 2, 3, ,}

1.
太原理工大学机械与运载工程学院应用力学研究所，山西太原 030024
2.
太原理工大学机械与运载工程学院材料强度与结构冲击山西省重点实验室，山西太原 030024
3.
太原理工大学机械与运载工程学院力学国家级实验教学示范中心，山西太原 030024

基金项目: 国家自然科学基金（51501123, 11390362）；山西省“1331工程”重点创新团队建设计划。

详细信息

作者简介:
马胜国（1983－　），男，博士，副教授，mashengguo.cumt@163.com

通讯作者:
王志华（1977－　），男，博士，教授，wangzh077@163.com

中图分类号: O347；TG146.4
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- 被引次数: 0
出版历程
- 收稿日期: 2020-08-24
- 修回日期: 2021-03-01
- 网络出版日期: 2021-10-25
- 刊出日期: 2021-11-23

Dynamic mechanical properties and constitutive relations of CoCrFeNiAl_xhigh entropy alloys

MA Shengguo^{1, 2, 3
,},
WANG Zhihua^{1, 2, 3
, ,}

1.
Institute of Applied Mechanics, College of Mechanical and Vehicle Engineering, Taiyuan University of Technology, Taiyuan 030024, Shanxi, China
2.
Shanxi Key Laboratory of Material Strength and Structural Impact, Taiyuan University of Technology, Taiyuan 030024, Shanxi, China
3.
National Experimental Teaching Demonstration Center of Mechanics, Taiyuan University of Technology, Taiyuan 030024, Shanxi, China

摘要

摘要: 高熵合金，以其独特的合金设计和优异的综合性能，成为当下材料研究的热点。本文利用高真空电弧熔炼法成功制备出了CoCrFeNiAl_x（x=0, 0.6, 1）系高熵合金，并通过分离式霍普金森压杆对其进行一系列不同应变速率下的动态压缩试验。通过X射线、扫描电镜和透射电镜分析，深入探索了该合金系的晶体结构、微观组织和变形特征。最后，利用修正后的Johnson-Cook (J-C)本构模型，获得了该体系高熵合金的动态本构关系。
- 高熵合金 /
- 动态冲击 /
- 本构关系 /
- 变形机理
Abstract: High-entropy alloys (HEAs), due to their unique alloy-design concepts and excellent comprehensive properties, are becoming a research hotspot nowadays. However, previous reports were scarcely focused on the dynamic mechanical loading of the HEAs, that is the applied strain rates often were limited in the quasi-static regime. In this research, CoCrFeNiAl_x HEAs were successfully prepared by vacuum arc melting pure elements in a high-purity argon atmosphere on a water-cooled Cu hearth. Each ingot was remelted at least five times to ensure its chemical homogeneity. Cylindrical samples with a diameter of three millimeters were then synthesized by copper-mould suction casting. Quasi-static compressive tests at room temperature were conducted by using an Instron 5969 testing machine, wherein the test specimens with an aspect ratio of 1∶1 were cut from the cylindrical samples along the longitudinal direction by electrical discharge machining. As a comparison, dynamic compression experiments with various strain rates were carried out at room temperature by the split Hopkinson pressure bar (SHPB). For characterization, crystal structure, microstructure and deformation characteristics were investigated in detail by a combination of X-ray diffraction (XRD), scanning-electron microscopy (SEM), and transmission-electron microscopy (TEM) analyses. The XRD results reveal that simple solid solution structures, in forms of face-centered cube (FCC) and/or body-centered cube (BCC), were obtained in the current alloys. All the alloys exhibit positive strain-rate sensitivity and excellent work-hardening ability. Interestingly, three isolated deformation mechanisms were detected by TEM analysis, that is combined dislocation slip plus deformation twinning dominats the plastic deformation in the CoCrFeNi alloy (with FCC structure) for both quasi-static and dynamic loading conditions, however, such phenomenon was only observed in the CoCrFeNiAl_0.6 alloy (with FCC plus BCC structure) under dynamic loading. As for the CoCrFeNiAl alloy (with BCC structure), single dislocation slip accounts for the plastic deformation in both quasi-static and dynamic loading conditions. Moreover, the dynamic constitutive relations of CoCrFeNiAl_x HEAs were obtained by the modified John-Cook (J-C) constitutive model.
- high-entropy alloy /
- dynamic loading /
- constitutive relation /
- deformation mechanism

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图 1 CoCrFeNiAl_x系高熵合金的XRD图谱

Figure 1. XRD patterns of CoCrFeNiAl_x high-entropy alloys

下载: 全尺寸图片幻灯片

图 2 CoCrFeNiAl_x系高熵合金的微观组织SEM图

Figure 2. SEM images of CoCrFeNiAl_xhigh-entropy alloys

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图 3 CoCrFeNiAl_x系高熵合金在不同应变速率下的工程应力-应变曲线

Figure 3. Engineering stress-strain curves of CoCrFeNiAl_x high-entropy alloys at various strain rates

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图 4 CoCrFeNiAl_x系高熵合金在两种不同区域下的屈服强度应变率敏感性

Figure 4. Strain-rate sensitivity of yield strength at two regions for CoCrFeNiAl_xhigh-entropy alloys

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图 5 CoCrFeNiAl_x系高熵合金的动态流变应力与相应J-C模型

Figure 5. Comparison between dynamic flow stresses and the J-C model of CoCrFeNiAl_x high-entropy alloys

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图 6 CoCrFeNi高熵合金在应变速率为1×10⁻⁴ s⁻¹下的TEM图

Figure 6. TEM images of the CoCrFeNi high-entropy alloy at the strain rate of 1×10⁻⁴ s⁻¹

下载: 全尺寸图片幻灯片

图 7 CoCrFeNi高熵合金在应变速率为2800 s⁻¹下的TEM图

Figure 7. TEM images of the CoCrFeNi high-entropy alloy at the strain rate of 2800 s⁻¹

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图 8 CoCrFeNiAl_0.6高熵合金在应变速率为1×10⁻⁴ s⁻¹和3 600 s⁻¹下的TEM图^[19]

Figure 8. TEM images of the CoCrFeNiAl_0.6 high-entropy alloy at the strain rates of 1×10⁻⁴ s⁻¹ and 3 600 s⁻¹

下载: 全尺寸图片幻灯片

图 9 CoCrFeNiAl高熵合金在不同应变速率下的TEM图^[25]

Figure 9. TEM images of the CoCrFeNiAl high-entropy alloy at different strain rates^[25]

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表 1 3种高熵合金在2种加载方式下的强化机制比较

Table 1. Comparison of strengthening mechanisms for the three HEAs under two loading conditions

合金	相组成	强化机制（低应变速率）	强化方式（高应变速率）
Al₀	FCC	位错+孪晶，具有TWIP效应	位错+孪晶，具有TWIP效应
Al_0.6	FCC	位错	位错+孪晶，具有TWIP效应
Al_0.6	BCC	位错	位错
Al₁	BCC	位错	位错

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