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Chromium alloys; Cobalt alloys; Deformation; Dynamics; Entropy; Grain boundaries; Grain size and shape; High resolution transmission electron microscopy; Iron alloys; Manganese alloys; Mechanical properties; Strain hardening; Tensile strength; Transmission electron microscopy, Deformation twinning; Dynamic deformation; Dynamic deformation behavior; Electron back scatter diffraction; High entropy alloys; Plastic stability; Tension and compression; Ultimate tensile strength, Strain rate
Abstract:
In this study, mechanical tests were conducted on a face-centered cubic FeCoNiCrMn high-entropy alloy, both in tension and compression, in a wide range of strain rates (10−4–104 s−1) to systematically investigate its dynamic response and underlying deformation mechanism. Materials with different grain sizes were tested to understand the effect of grain size, thus grain boundary volume, on the mechanical properties. Microstructures of various samples both before and after deformation were examined using electron backscatter diffraction and transmission electron microscopy. The dislocation structure as well as deformation-induced twins were analyzed and correlated with the measured mechanical properties. Plastic stability during tension of the current high-entropy alloy (HEA), in particular, at dynamic strain rates, was discussed in lights of strain-rate sensitivity and work hardening rate. It was found that, under dynamic conditions, the strength and uniform ductility increased simultaneously as a result of the massive formation of deformation twins. Specifically, an ultimate tensile strength of 734 MPa and uniform elongation of ∼63 are obtained at 2.3 × 103 s−1, indicating that the alloy has great potential for energy absorption upon impact loading. © 2018 Science China Press
