On the possibility to reduce ECAP deformation temperature in magnesium: Deformation behaviour, dynamic recrystallization and mechanical properties

This work investigates the effect of temperature on the dynamic recrystallization (DRX) behaviour and its consequence on the microstructure, texture, and mechanical properties in pure magnesium during equal channel angular pressing (ECAP) by route-A up to eight passes (epsilon(Eff) = 9.3). The ECAP temperature was reduced in steps for gradual grain refinement. Thereby the 8th pass could be conducted successfully at 200 degrees C, 150 degrees C and 27 degrees C, respectively. Irrespective of the 8th pass ECAP temperature, similar to 0.30 microstructure fraction was found to be DRXed. Continuous dynamic recovery and recrystallization (CDRR) predominantly occurred, resulting in the formation of fine grains with the necklace structure for all the conditions. However, distinctive and abnormally coarse CDRR grains evolved irrespective of the ECAP temperature. CDRR lead to the formation of Sigma 13a boundaries with [0002]-30 degrees axis-angle pair. Discontinuous DRX was also observed intermittently in the ECAP microstructures. The average grain size after the 8th pass ECAP at 200 degrees C, 150 degrees C and 27 degrees C was similar to 2.6 mu m, similar to 1.4 mu m and similar to 0.75 mu m mu m, respectively. The yield strength increases and the ultimate compressive strength (UCS) as well as strain to failure, decreases with grain refinement. The ambient temperature compressive strain hardening behaviour was initially sigmoidal, attributing to the evolution of {10 (1) over bar2}(1) over bar 011 extension twins. Sigmoidal flow behaviour reduces gradually as the grain size decreases with ECAP. No sigmoidality indicate slip-dominated deformation after 8th pass ECAP at 150 degrees C and 27 degrees C.