A Review Study on the Main Sources of Porosity in Al-Si Cast Alloys

The present study was performed on A356 and B319 alloys in mechanically stirred or degassed condition. Melts were Sr-modified grain-refined. Hydrogen content varied from less than 0.1 ml/100 g Al to ∼0.4 Al; Fe increased 0.8% alloy. Lanthanum cerium added as 99.5% pure metals. Two main techniques used investigate porosity formation: fracture surface of tensile fatigue test bars, reduced pressure (RPT) method. Porosity type shape examined. results show that pore size is more influential small scattered ones a mechanical point view. Tensile testing affected by located at the center bar, whereas edge responsible for crack initiation case testing. Intermetallics precipitate form intercepted platelets which restricts flow molten metal, leading formation shrinkage cavities. Precipitation clusters compounds liquid state such Al2Si2Sr, Mg2Sn, Al3Ti, Al2O3particles would well act nucleation sites formation. Most oxides observed long branched strings. In some cases, bifilms also reported addition SrO MgO.