Estimating toughness limit of cast aluminum alloys with Reduced Pressure Test

The mechanical properties of cast aluminum alloys are affected by extrinsic and intrinsic defects. The most critical ones that deteriorate the toughness of aluminum and its alloys are known to be the dissolved hydrogen and oxide inclusions. It has been shown that folded oxide skins (also known as bifilms) have the most pronounced effect when it comes to mechanical properties. The first rule of casting begins with the start of a clean melt which followed by the quiescent mold filling in order to achieve defect-free, high quality cast aluminum alloys. In this work, a design of a mold that produces 10 cylindrical bars was evaluated to assess the effects of both melt cleanliness and also the mold filling in a well-designed runner system. The design was proposed to reveal the potential toughness limit of aluminum alloys, while eliminating the effect of extrinsic defects. A correlation between melt cleanliness measurement by reduced pressuretest/RPT (bifilm index) and tensile properties was also proposed.