Mechanical Response and Microstructure Evolution of a Repetitive Upsetting Extrusion Processed AZ61 Magnesium Alloy in Semi‐Solid Compression

Abstract

Semi‐solid billets of an AZ61 magnesium alloy are prepared by a repetitive upsetting‐extrusion (RUE)‐based strain induced melt activation (SIMA) method. Mechanical response and microstructure evolution in compression of the semi‐solid slurry with high solid fraction are investigated. The results reveal that the SIMA‐processed thixotropic structure comprises of globular solid particles and liquid films. True stress–true strain curves experience a rapid increase to the peak within a small strain, a slow decline, and the final steady‐state flow. Three regions of the dense deformation region, the severe deformation region, and the free deformation region are detected in the compressed specimen with reference to microstructure observation. Liquid segregation is found in the free deformation region due to the exudation of the liquid phase. The compression of the semi‐solid slurry is achieved by the coordination of the solid particles’ rearrangement and the liquid flow. The initial deformation stage is governed by the sliding or rotating of the solid particles. Mechanisms of the sliding between solid particles and the plastic deformation of the solid particles are responsible for the second and the final deformation stages, and their relative contribution is closely related to the solid fraction and deformation strain.

Effects of Process Parameters on the Microstructure and Hardness of Semi-Solid AlSi9Mg Aluminum Alloy Prepared by RAP Process

“…During the RAP process, the semi-solid billet is fabricated by heating the deformed alloy up to the semi-solid value and holding this temperature for a certain time required. The technologies mostly applied for the deformation in the RAP process include the equal channel angular extrusion, 15) accumulative plastic deformation, 16) repetitive upsetting-extrusion, 17) compression 18) and extrusion. 19) The microstructural evolution of different semi-solid alloys has been investigated by many studies as it significantly affects the mechanical property of the final product.…”