Crystal plasticity finite element analysis of NiCoCrFe high entropy alloy considering dislocation density and damage

Abstract

Macroscopic and microscopic mechanical responses, damage behavior and microstructure evolution of NiCoCrFe high entropy alloys (HEAs) during finite deformation under quasi-static loading were investigated by experiments and crystal plasticity finite element method. The microstructure of NiCoCrFe before and after tensile deformation was characterized by electron backscattering diffraction technique(EBSD). The internal state variables of dislocation density and continuum damage factors were introduced into the CPFEM model by modifying the strengthening model and the flow criterion, and the NiCoCrFe related model parameters were determined by combining the stress-strain curves of the tensile test. The results show that the CPFEM model considering the dislocation density and damage can effectively describe the macroscopic and microscopic mechanical responses of NiCoCrFe. CPFEM model can reasonably predict the deformation shape and size of NiCoCrFe necking region, among which, the length of the necking region obtained in the experiment is 7% smaller than the predicted result, and the width of the necking region predicted by CPFEM is 23% larger than the experimental result. The texture evolution predicted by CPFEM model after NiCoCrFe tensile deformation is in good agreement with the results that characterized by EBSD, showing weak (100)//RD and strong (111)//RD fiber texture. In the analysis of the 3D micro- structure damage, the damage predicted by the current CPFEM model appears as an inter-granular damage mechanism at the grain boundary where stress and dislocation density are concentrated, and the damage gradually expands to the grain interior with the increase of deformation.

Keywords

• high entropy alloy
• crystal plasticity finite element
• damage
• dislocation density
• texture