Study on the Dynamic Shear Properties and Texture Evolution of CoCrNiSi0.3 Medium-Entropy Alloy

Abstract

The dynamic loading of CoCrNiSi0.3 medium-entropy alloys was performed by using Split Hopkinson Pressure Bar. The compression properties at different strain rates were investigated, and found to be sensitive to strain rates and have obvious strain rate strengthening effect. Under quasi-static compression (strain rate 10-4 s-1), the strain rate sensitivity m is 0.13, while under dynamic compression (strain rate 5 150 s-1) m 0.25. The shear properties of the alloy were studied through hat shaped shear test. The results show that the quasi-static shear yield strength is 330 MPa and the dynamic shear yield strength is 630 MPa. With the increase of the width of the reserved shear region, the peak stress decreases, but the shear failure strain increases obviously. When the width of the reserved shear region is 50 μm, the shear strain is as high as 12.8. Through the shear “freezing” experiment, the effect of increasing shear deformation on the grain microstructure and texture evolution of the material was studied. The results show that the geometric dislocation density in the grain increases with the increase of deformation, and the deformation texture evolves to A and P type texture, while the Cu type texture decreases gradually. Before the formation of adiabatic shear band, the temperature rise calculated by power-heat conversion lacks accuracy, which proves that the formation of adiabatic shear band is not caused by thermal softening.

Keywords

• medium/high-entropy alloy
• adiabatic shear
• mechanical properties
• texture evolution