A comprehensive analysis of cooling curves, fluidity, inclusions, porosity, and microstructure of NaCl-KCl-NaF flux treated Al-12Si alloy

Abstract In this study, we investigated the effects of treating Al-12 wt% silicon alloy with an equimolar composition mixture of NaCl, KCl, and NaF on various aspects of the alloy’s properties. Key findings of the research indicate that the flux treatment had significant effects on the alloy. It led to increased nucleation temperatures and reduced undercooling, thereby facilitating nucleation sites and grain refinement. Additionally, the inclusion of flux reduced the entrapment of inclusions in the melt, which can potentially enhance the mechanical properties of the alloy. However, it also led to a larger and more widely distributed gas porosity in the solidified samples, as gas evolved from the flux trapped during solidification. Moreover, the flux treatment had noticeable impacts on the morphology of eutectic silicon particles, reducing their aspect ratio. These findings offer valuable insights into the potential benefits and challenges of sodium-based flux melt treatment in optimizing the quality of Al-12Si alloy castings, particularly in die-casting applications.