During our experiments, we conducted multiple rotary degassing treatments with Ar and N2 purging gases on a 356 alloy with 200 ppm Sr. We found that the fading process of the added modifier is accelerated when nitrogen was used (The Sr concentration decreased and the thermal analysis results showed lower eutectic undercooling). Is it possible that nitrogen forms a compound with the strontium present in the melt? We found no thermodynamic data available for strontium nitrides with various stochiometry, so we could not calculate Gibbs energy of formation values at different temperatures.
The FactSage databases contain at least information about Sr3N2, but in liquid aluminum, the program predicted, that the formation of AlN is more likely compared to the formation of Sr3N2.
Thank you Marcus Sommerfeld ! I managed to find some thermochemical data for Sr3N2 and based on the results of my calculations I came to the same conclusion. I think we should do an XRD analysis on the dross in order to identify the phases formed during the treatment.
Hello,
No here the nitrogen gas does not react it is inert it is quite like the case where it adds the role of carrier gas in CPG.
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