A. Khakzadshahandashti - Department of Materials Science and Engineering, Sharif University of Technology, Tehran, Iran
N. Varahram - Department of Materials Science and Engineering, Sharif University of Technology, Tehran, Iran
P. Davami - Department of Materials Science and Engineering, Sharif University of Technology, Tehran, Iran
M. Pirmohammadi - Department of Mechanical Engineering, Pardis Branch, Islamic Azad University, Tehran, Iran

The combined influence of both melt filtration and cooling rate on the microstructure features and mechanical properties of A۳۵۶ cast alloy was studied. A step casting model with five different thicknesses was used to obtain different cooling rates. The effect of melt filtration was studied by using of ۱۰ and ۲۰ ppi ceramic foam filters in the runner. Results showed that secondary dendrite arm spacing decreased from ۸۰ μm to ۳۴ μm with increasing cooling rate. Use of ceramic foam filters in the runner led to the reduction of melt velocity and surface turbulence, which prevented incorporation of oxide films and air in the melt, and consequently had an overall beneficial effect on the quality of the castings. A matrix index, which is the representative of both SDAS and microporosity content, was defined to consider the simultaneous effect of melt filtration and cooling rates on UTS variations. Also, the fracture surface study of test bars cast using ۱۰ and ۲۰ ppi ceramic foam filters showed features associated with ductile fracture.

Aluminum alloys, microstructure, tensile properties, defects