Effects of strain rate on room- and cryogenic-temperature compressive properties in metastable V10Cr10Fe45Co35 high-entropy alloy

Hyejin Song,Dae Woong Kim,Yong Hee Jo,Sunghak Lee,Hyoung Seop Kim,Min Cheol Jo,Wooyeol Kim,Dong Geun Kim,Byeong-Joo Lee

doi:10.1038/s41598-019-42704-x

Abstract

Quasi-static and dynamic compressive properties of an FCC-based metastable HEA (composition; V10Cr10Fe45Co35 (at.%)) showing both Transformation Induced Plasticity (TRIP) and TWinning Induced Plasticity (TWIP) were investigated at room and cryogenic temperatures. During the quasi-static and dynamic compression at room temperature, the FCC to BCC TRIP occurred inside FCC grains, and resulted in very high strain-hardening rate and consequently maximum compressive strength over 1.6 GPa. The dynamic compressive strength was higher by 240 MPa than the quasi-static strength because of strain-rate-hardening effect, and kept increasing with a high strain-hardening rate as the twinning became activated. The cryogenic-temperature strength was higher than the room-temperature strength as the FCC to BCC TRIP amount increased by the decrease in stability of FCC phase with decreasing temperature. Under dynamic loading at cryogenic temperature, twins were not formed because the increase in SFE due to adiabatic heating might not be enough to reach the TWIP regime. However, the dynamically compressed specimen showed the higher strength than the quasi-statically compressed specimen as the strain-rate-hardening effect was added with the TRIP.

Highlights

Preservation, development, and transportation of resources have demanded novel metal alloys having excellent mechanical properties for technological advances and applications to extreme environments
Quasi-static and dynamic compressive properties of an FCC-based metastable high-entropy alloys (HEAs) showing both TRansformation Induced Plasticity (TRIP) and TWinning Induced Plasticity (TWIP) were investigated at room and cryogenic temperatures by using a universal testing machine and a split Hopkinson pressure bar, respectively, in this study
Quasi-static and dynamic compressive properties of an FCC-based metastable V10Cr10Fe45Co35 HEA showing both TRIP and TWIP were investigated at room and cryogenic temperatures, and a transition of TRIP and TWIP mechanisms was examined by detailed microstructural evolutions

Summary

Introduction

Preservation, development, and transportation of resources have demanded novel metal alloys having excellent mechanical properties for technological advances and applications to extreme environments. Recently-developed face-centered-cubic(FCC)-based high-entropy alloys (HEAs) provide excellent cryogenic-temperature strength, ductility, and fracture toughness by actively generating a TWinning Induced Plasticity (TWIP) mechanism[3,4,5,6]. Though the definition and utilization of SFE are difficult in FCC-based HEAs, the transition in deformation mechanisms might occur with decreasing temperature, and can directly affect their cryogenic-temperature properties[15]. Dynamic deformation researches are essentially needed for cryogenic or extreme applications of HEAs to enhance quasi-static and dynamic mechanical properties and to understand dynamic deformation behavior. Quasi-static and dynamic compressive properties of an FCC-based metastable HEA showing both TRIP and TWIP were investigated at room and cryogenic temperatures by using a universal testing machine and a split Hopkinson pressure bar, respectively, in this study. A transition phenomenon of TRIP and TWIP mechanisms occurring under different loading conditions and test temperatures was examined

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Conclusion