On-line prediction of the melt hydrogen and casting porosity level in 319 aluminum alloy using thermal analysis

One of the major problems associated with aluminum castings is the porosity. Porosity is attributed to the shrinkage process and a lack of interdendritic feeding, which result in a reduction of the mechanical properties, loss of pressure tightness and poor surface integrity in castings.In this research was developed a methodology for on-line prediction of the hydrogen and porosity levels in 319 melts and castings, respectively. The main tools used for this research were thermal analysis and image analysis. Thermal analysis revealed that the nucleation temperature for the Al–Si–Cu eutectic changed in up to 12.3 °C for a range of dissolved hydrogen from 0.06 to 25 mL H2/100 g Al. The hydrogen–porosity threshold determined for the 319 alloy was ∼0.15 mL H2/100 g Al in the low pressure conditions (6 kPa). A statistical analysis demonstrated that this technology is highly accurate (R2 = 0.91) to predict the amount of hydrogen and the porosity.