Study on hot deformation behaviour and microstructure of CoCrFeMnNi HEA using constitutive modeling and processing map

Aktiviteetti: Konferenssiesitelmä

Description

The constitutive flow behavior of CoCrFeMnNi high entropy alloy (Cantor alloy) was investigated by means of isothermal compression testing in the temperature and strain rate ranges of 1023–1423 K and 10−3–10 s−1, respectively. Constitutive equations were developed based on hyperbolic-sinusoidal Arrhenius-type modeling. The influence of deformation parameters was further characterized in respect of Zener-Hollomon parameter. The impact of true strain ranging from 0.2 – 0.75 was expressed via determination of material constants. The third order polynomial was considered appropriate to fit true-strain dependency of these material constants. A comparison of experimental and predicted flow stress curves showed a correlation factor of 0.9858 with the average absolute relative error (AARE) of 7.63%.
Additionally, the hot workability of cantor alloy was characterized through the construction of processing maps based on the principles of dynamic materials modeling (DMM). A ‘safe’ processing window was identified in the temperature and strain rate ranges of 1223–1373 K and 10−2 – 5×10−1 s−1, respectively, with a peak power dissipation efficiency of ~34% at 1293K and 3x10−2 s−1. Dynamic recrystallization (DRX) was found to be the dominant mechanism in this domain. Other deterministic domains too were suitably characterized. In the instability regime, grain boundary cracking/sliding and localized shear bands manifested below 1223 K and 10−2 s−1. At higher strain rates, intense adiabatic shear banding occurred along with the formation of voids. The instability regime further extended to high temperatures and strain rates up to 10 s-1. For instance, an increase in deformation temperature at high strain rates facilitated the occurrence of DRX in the shear bands. The characterization of constitutive flow behavior and identification of safe processing window in the temperature-strain rate space significantly improved our understanding of the hot workability of Cantor alloy to enable defect-free processing that would facilitate microstructural reconstitution for enhanced mechanical properties.
Aikajakso15 syyskuuta 2021
Tapahtuman otsikkoEUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES
Tapahtuman tyyppiConference
Tunnustuksen arvoInternational

Publication forum classification

  • Jufo-taso 0

Nature of activity

  • Tutkimuksellinen