Effective Degassing for Reduced Variability in High-Pressure Die Casting Performance

The reduced solubility of hydrogen in molten aluminium is believed to be a key factor influencing the formation of gas porosity, which adversely affects the mechanical properties. In this study, two crucibles of AlSi10MnMg alloy were degassed using conventional rotary degassing and high shear melt conditioning (HSMC) respectively and then cast into tensile specimens using the high-pressure die casting (HPDC) process. An optimal holding time of 10 min was established for both processing techniques corresponding to reduced density index (DI) and reduced variation in tensile performance. After rotary degassing, DI values were found to increase with increasing holding times, rising to 4.1% after 70 min. For HSMC, a quasi-steady state was observed with a maximum DI value of 1.4% after 190 min. The pore size in HPDC cast specimens was observed to be considerably lower after degassing with the HSMC device compared with rotary degassing.