Effect of Chip Size on Semi-Solid Microstructure of AZ91D Magnesium Alloy Prepared by CRP Process

Abstract

In this paper, chip recycled pressing process (CRP for short), a new method for recycling magnesium alloy chips, was put forward to prepare semi-solid billet. AZ91D magnesium alloy chips of different sizes were respectively recycled to prepare semi-solid billet by CRP process. Effect of chip size on compactness, microstructure and oxidation of CRP billet were investigated. And then CRP billet were heated to semi-solid state and its semi-solid microstructures were studied. The results showed that with the increase of chip thickness, grain refinement effect weakened, deformation uniformity aggravated and oxygen content of CRP billet decreased. Under the same CRP process conditions, the relative densities of four kind of CRP billet were 98.27%, 98.13%, 98.05% and 97.92%, respectively. Meanwhile, there was no significant difference in compactness and microstructure between them. Normally, oxygen content was not more than 1.8% and uniformly dispersed in CRP billet. Hence, the influence of size and deformation inhomogeneity of chip on compactness and microstructure of CRP billet were eliminated via CRP process. In CRP billet, microstructure and strain were uniform and this inherited during semi-solid isothermal treatment.