High-temperature compressive behavior and kinetics analysis of Al0.4MnCrCoFeNi high entropy alloy

Abstract

In the present study, AlxMnCrCoFeNi alloys (x = 0, 0.4) were produced by vacuum melting and casting. For this aim, ingots were subjected to the homogenization, cold roll, and annealing. X-ray diffraction analysis and SEM images indicated that the crystal structure is FCC solid solution for MnCrCoFeNi. Moreover, in addition to FCC solid solution, the alloy with aluminum (x = 0.4) ordered B2 precipitates. Besides, hot compressive tests were conducted at different temperatures and strain rates of 0.01, 0.05 and 0.1/s. Investigating the stress-strain diagrams and work hardening rate, it was revealed that twins played a role in the deformation mechanism. In the constitutive equation, the values of the stress exponent and activation energy were measured and they were 6.86 and 434 kJ mol-1, respectively. The exponential equations of peak stress and peak strain, as well as steady-state stress, were obtained due to the Zener-Hollomon parameter. Regarding the linear relationship between the work hardening rate and the dislocation annihilation coefficients, the activation energy of deformation changes at 600 C. Finally, another effect of the Al addition was shown to be increase in initiation temperature of necklace structure about 200 C in hot compression test. In addition, B2 nanoprecipitate and nanotwins indicated that there was twin deformation mechanism in alloy containing Al.