Shear localization of fcc high-entropy alloys

Marc A Meyers,Bingfeng Wang,Shiteng Zhao,Yong Liu,Zezhou Li,Peter K Liaw,E Buzaud,H Couque,A Cosculluela,E Cadoni

doi:10.1051/epjconf/201818303028

Abstract

Dynamic behavior of the single phase (fcc) Al0.3CoCrFeNi and CoCrFeMnNi high-entropy alloys (HEAs) was examined. The combination of multiple strengthening mechanisms such as solid solution hardening, cutting forest dislocation, as well as mechanical nano-twinning leads to a high work-hardening rate, compared with conventional alloys. The resistance to shear localization was studied by dynamicallyloading hat-shaped specimens to induce forced shear localization. However, no adiabatic shear band could be observed for Al0.3CoCrFeNi HEA at a large shear strain ~1.1. Additionally, shear localization of the CoCrFeMnNi HEA was only found at an even larger shear strain ~7 under dynamic compression. It is therefore proposed that the combination of the excellent strain-hardening ability and modest thermal softening of these two kinds of high-entropy alloys gives rise to remarkable resistance to shear localization, which makes HEAs excellent candidates for impact resistance applications.

Highlights

Adiabatic shear localization is recognized as an important failure mechanism of materials and is produced by the temperature rise in a narrow region, especially formed under high strain-rate deformation, when the deformation time is lower than the heat diffusion time [1]
The presence of annealing twins is inversely related to the stacking fault energy which is very low in high-entropy alloys [6]
These two kinds of single phase high-entropy alloys were subjected to dynamic loading to examine their dynamic properties, such as strength, and deformation mechanisms, especially on shear localization

Summary

Introduction

Adiabatic shear localization is recognized as an important failure mechanism of materials and is produced by the temperature rise in a narrow region, especially formed under high strain-rate deformation, when the deformation time is lower than the heat diffusion time [1]. Cantor et al [2] developed the CrMnFeCoNi HEA with the single face-centered-cubic (fcc) phase and this alloy is known as the Cantor alloy. Its mechanical properties improved at cryogenic temperatures due to the transition of deformation mechanism from planar dislocation slip to mechanical nanotwinning. This excellent strainhardening ability at cryogenic temperature (77 K) results in outstanding combinations of strength and ductility of the Cantor alloy. Dynamic properties of fcc (face-centered-cubic) high-entropy alloys, especially shear localization, are still unexplored

Experimental procedures

Results and discussion

Conclusions