Dynamic mechanical properties and constitutive relations of CoCrFeNiAlx high entropy alloys

MA Shengguo; WANG Zhihua

doi:10.11883/bzycj-2020-0293

Volume 41 Issue 11

Nov. 2021

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MA Shengguo, WANG Zhihua. Dynamic mechanical properties and constitutive relations of CoCrFeNiAlx high entropy alloys[J]. Explosion And Shock Waves, 2021, 41(11): 111101. doi: 10.11883/bzycj-2020-0293

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MA Shengguo, WANG Zhihua. Dynamic mechanical properties and constitutive relations of CoCrFeNiAl_xhigh entropy alloys[J]. Explosion And Shock Waves, 2021, 41(11): 111101. doi: 10.11883/bzycj-2020-0293

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Dynamic mechanical properties and constitutive relations of CoCrFeNiAl_xhigh entropy alloys

doi: 10.11883/bzycj-2020-0293

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

Received Date: 2020-08-24
Rev Recd Date: 2021-03-01

Available Online: 2021-10-25

Publish Date: 2021-11-23

Abstract

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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References(25)

References

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