EFFECTS OF PROCESSING PARAMETERS ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF Al-Si-Cu ALLOY AFTER VACUUM SUCTION CASTING

High performance of complex thin-walled parts based on bottom-hole vacuum suction casting (VSC) has drawn considerable research interest. Here, we report on the preparation of Al-7Si-4.5Cu-0.15Mg-0.1Ti alloy castings with the use of different VSC processing parameters. The microstructure and mechanical properties of the castings were analyzed with scanning electron microscope imaging, a universal tensile tester and a microhardness tester. Our experimental results showed that the microstructure of the castings was relatively compact. When the negative differential pressure increased, the number of primary Si flakes decreased and the distribution of the alpha(Al) + Si eutectic became more uniform and better oriented. Apparent shrinkage and looseness of the morphology also decreased. When the suction diameter was decreased, the apparent microporosity decreased at first and then increased. The distribution of the eutectic Si flakes became more uniform at first and then more chaotic. A suction diameter of 3 mm and negative differential pressure of 0.08 MPa gave the best mechanical properties, namely a tensile strength of 195.8 MPa, elongation at break of 14.093 % and microhardness of 107.3 HV.