Constitutive modelling of hot deformation behaviour of a CoCrFeMnNi high-entropy alloy

Abstract

Models describing the constitutive flow behaviour of a metallic material are desired for appropriate process design and realization of defect-free components. In this study, constitutive equations based on the hyperbolic-sinusoidal Arrhenius-type model have been developed to define the hot deformation characteristics of a CoCrFeMnNi high-entropy alloy. The experimental true stress-true strain data were generated over a wide temperature (1023-1423 K) and strain rates (10 −3-10 s −1) ranges. The impact of strain rate and temperature on deformation behaviour was further characterized through a temperature compensated strain rate parameter, i.e. Zener-Hollomon parameter. Additionally, a mathematical relation was employed to express the influence of various material constants on true-strain ranging from 0.2 to 0.75. Typical third order polynomial relations were found to be appropriate to fit the true-strain dependency of these material constants. The accuracy of the developed constitutive equations was evaluated by using the average absolute relative error (AARE) and correlation coefficient (R); the obtained values were 7.63% and 0.9858, respectively, suggesting reasonable predictions. These results demonstrate that the developed constitutive equations can predict the flow stress behaviour of the alloy with a good accuracy over a wide range of temperature and strain rate conditions and for large strains.

Hot Deformation Behavior of Cu–Sn–La Polycrystalline Alloy Prepared by Upcasting

“…By the Zener–Holloman parameter (Z), that is, the temperature-compensated strain rate, the relationship between the temperature and the strain rate corresponding to plastic deformation can be analyzed. According to Equation (1) [ 30 ], the respective constitutive equation can be expressed as follows: …”

Microstructure Refinement of a Transformation-Induced Plasticity High-Entropy Alloy

“…On the other hand, the apparent activation energy for the hot-deformation of the Co 35 Cr 25 Ni 15 Mn 15 Fe 10 TRIP-HEA was 385.7 kJ/mol, which is slightly higher than that of the Cantor HEA (~350 kJ/mol) [ 17 , 18 , 19 , 20 ]. The activation energies of pure aluminum, copper, and nickel are 142, 197, and 285 kJ/mol, respectively [ 24 , 46 ].…”

“…On the other hand, the recrystallized grains did not exhibit a strong texture. The apparent activation energy of the Cantor HEA is approximately 350 mJ/mol [ 17 , 18 , 19 , 20 ], which is close to that of the diffusion of Ni in the system [ 23 , 24 , 25 ]. The steady-state deformation is controlled by the dislocation climb [ 25 ].…”

“…Recently, the deformation behavior of the CoCrFeMnNi HEA and the CoCrNi medium entropy alloy at a temperature higher than 1073 K was investigated, and the constitutive relationships between the flow stress, strain, strain rate, and temperature were clarified [ 17 , 18 , 19 , 20 , 21 , 22 ]. Research reported that the evolution of grain structure is accompanied by the discontinuous dynamic recrystallization (dDRX), in which the newly recrystallized grains were referred to the form at the original grain boundaries (GBs) [ 17 , 18 , 19 , 20 , 21 , 22 ].…”

High-Temperature Deformation Behaviors of the C-Doped and N-Doped High Entropy Alloys

“…It was reported that discontinuous dynamic recrystallization (dDRX) notably contributed to grain refinement during hot-deformation, in which the recrystallized grains tend to nucleate at the primary grain boundaries (GBs) [14,24]. The apparent activation energy of the Cantor HEA is close to that of the diffusion of Ni in the alloy, and the dislocation climb determines the steady-state deformation [25][26][27][28][29][30][31][32]. Even though the DRX behaviors of CoCrNi MEA and the novel Co-rich TRIP HEA were investigated in our previous studies [14,24], the influence of interstitial atoms such as C and N on hot-deformation and grain structure evolution have not been clarified.…”