A comparative study on the microstructural evolution in AM60 alloy processed by ECAP and MDF

Extruded AM60 Mg alloy samples were processed by two different severe plastic deformation (SPD) techniques, equal-channel angular pressing (ECAP) and multi-directional forging (MDF) at 220 °C for 2, 4 and 6 passes. The evolutions of the microstructure during ECAP and MDF were compared. It was found that although the main trends were similar for the two processing methods, the changes in the microstructure were more pronounced for ECAP. This effect was explained by the higher imposed strain and the different loading conditions applied during ECAP, which resulted in a much larger dislocation density and precipitate fraction for 2 passes compared to MDF. Between 2 and 6 passes, the dislocation density decreased, while the diffraction domain size increased due to recovery/recrystallization. The present study demonstrates that for the two SPD-processing methods the microstructural evolutions do not coincide either as a function of the number of passes or the equivalent strain.