Study of Dynamic Precipitation during Severe Plastic Deformation of Cast AZ91 Alloy and Its Influence on Microstructure and Mechanical Properties

In this study severe plastic deformation was applied to a typical as-cast AZ91 alloy through equal channel angular pressing. The equal channel angular pressing of AZ91 alloy was carried out as a two-step process in which the first equal channel angular pressing pass was conducted at 350° Cand the next passes were followed at 290°. The equal channel angular pressing processing could strongly refine the grains. The results showed that dynamic precipitation and dynamic recrystallization occurred simultaneously leading to an enhancement of the recrystallization process. Microstructural investigations indicated that the formation of precipitates starts at shear zone as a result of the large shear strains and high density of dislocations. The analysis of tensile test results showed that the equal channel angular pressing can significantly improve both yield strength and ductility of AZ91 alloy.