Gravity effects on reactive settling of transition metals in liquid aluminum under SHS conditions

The reactive settling of W, Ta, Ni, and Ti in liquid aluminum was investigated under terrestrial and microgravity conditions. Settling occurred in some systems and total dissolution occurred in others. Analyses were made based on Stoke’s settling time relative to dissolution time based on two approaches: dissolution based on a diffusion-controlled process and based on solubility limit. The experimental results are in agreement with the solubility model. The effect of solid volume fraction was also investigated. The results showed a critical volume fraction of about 20 vol.%, in agreement with literature values. Effect of particle size was investigated and the observations are consistent with the analysis of settling and dissolution times, indicated above. The absence of settling of the intermetallic phases in all systems was attributed to solid skeleton formation, and confirmed by results on low solid content experiments.