Microstructure and Mechanical Properties of A356 Aluminum Alloy Prepared by Casting Combined with Back Extrusion

In this paper, the microstructure and mechanical properties of A356 aluminum alloy prepared by the combined forming process of casting and back extrusion are investigated. The back extrusion was employed to induce severe plastic deformation for improving the casting microstructures at temperatures ranging from 490 to 540°С with different feed rates. Many shrinkage porosities were found in the original casting samples. According to the experiments carried out in this paper, the combined process could significantly eliminate the shrinkage porosities. The plate-like or long strip-like Si particles and the primary casting dendrites could be obviously refined at the region where the effective strain is larger than 1.8. The severe plastic deformation could be induced at the region under the punch, where the microstructure refining was achieved at the same time. Due to the softening behavior caused by dynamic recovery, the yield strength and compressive strength of the deformed area gradually decreased with the feed rate, while they increased as the pressure gradually increased at the undeformed region.