Experimental and simulation research on hollow AZ31 magnesium alloy three-channel joint by hot extrusion forming with sand mandrel

Magnesium alloy is one of the lightest metal structural materials. The weight is further reduced through the hollow structure. However, the hollow structure is easily damaged during processing. In order to maintain the hollow structure and to transfer the stresses during the high temperature deformation, the sand mandrel is proposed. In this paper, the hollow AZ31 magnesium alloy three-channel joint is studied by hot extrusion forming. Sand as one of solid granule medium is used to fill the hollow magnesium alloy. The extrusion temperatures are 230 °C and 300 °C, respectively. The process parameters (die angle, temperature, bottom thickness, sidewall thickness, edge-to-middle ratio in bottom, bottom shape) of the hollow magnesium alloy are analyzed based on the results of experiments and the finite element method. The results are shown that the formability of the hollow magnesium alloy will be much better when the ratio of sidewall thickness to the bottom thickness is 1:1.5. Also when edge-to-middle ratio in bottom is about 1:1.5, a better forming product can be received. The best bottom shape in these experiments will be convex based on the forming results. The grain will be refined obviously after the extrusion. Also the microstructures will be shown as streamlines. And these lines will be well agreement with the mold in the corner.