Effects of Casting Pressurization Pressure on Microstructure and Mechanical Properties of AlSi9Mg Aluminum Alloy for Automobile

The effects different pressurization pressures on the microstructure and mechanical properties of AlSi9Mg alloy were studied by changing the pressure during low pressure casting. The results show that the AlSi9Mg alloy samples prepared at high pressurization pressure have a denser microstructure and more spherical eutectic Si particles. At the same time, due to the better filling ability, the pore defects of the alloy under high pressurization pressure are greatly reduced, and the alloy has more excellent mechanical properties.At three different levels of pressurization pressure of 90, 150, and 210 kPa, the grain size gradually decreases, and the grain size and secondary dendrite arm spacing of the corresponding alloys are 246, 197, 149 μm and 44.9, 37.3, 31.1 μm, respectively. The density and porosity corresponding to the three pressurization pressures are 2.656, 2.659, 2.674 g/cm³ and 0.96%, 0.79%, 0.38%, respectively. The tensile strength, yield strength and elongation of the AlSi9Mg alloy are 238.76, 174.68 MPa and 3.14%; 252.43, 177.47 MPa and 4.61%; 256.10, 178.81 MPa and 6.85%, respectively, increasing by 7.26%, 2.36% and 118.15%, respectively.