Microstructural Evolution of UFG Magnesium Alloy Produced by Accumulative Back Extrusion (ABE)

Abstract

Accumulative back extrusion (ABE) is a recently developed severe plastic deformation process. In this article, the effects of deformation ratio (inner punch diameter/outer punch diameter) employed for ABE on the microstructure, grain size distribution, and Mg17Al12 phase precipitation in AZ91 magnesium alloys were investigated. The results showed that the deformation ratio has significant effect on the microstructure of processed material. Also, increasing in the deformation ratio leads to better microstructure homogeneity, more grain refinement, and more Mg17Al12 precipitation. Quantitative grain size value showed that the minimum grain size value corresponds to the center zone of ABE processed sample with higher deformation ratio. The massive Mg17Al12 precipitates remaining in the matrix increase by decreasing the deformation ratio. Microhardness observation verified the microstructure results.