Mechanical properties and microstructures of Al alloy tensile samples produced by serpentine channel pouring rheo-diecasting process

An innovative one-step semi-solid processing technique of A356 Al alloy, the serpentine channel pouring rheo-diecasting process (SCRC), was explored. The mechanical properties and microstructures of the tensile samples made by the SCRC technique were tested in the as-cast and T6 heat treatment conditions. The experimental results show that the as-cast ultimate tensile strength can reach about 250 MPa and the elongation is 8.6%-13.2%. The ultimate tensile strength can increase approximately 30% higher than that of the as-cast one but there is some slight sacrifice of the plasticity after T6 heat treatment. Under these experimental conditions, the semi-solid A356 Al alloy slurry with primary alpha(1)(Al) grains, which have the shape factor of 0.78-0.89 and the grain diameter of 35-45 mu m, can be prepared by the serpentine channel pouring process. The primary alpha(2)(Al) grains are very fine during the secondary solidification stage. Compared with the conventional HPDC process, the SCRC process can improve the microstructures and mechanical properties of the tensile test samples. The advantages of the SCRC process include easily incorporating with an existing HPDC machine, cancelling the preservation and transportation process of the semi-solid alloy slurry, and a higher cost performance.