A new approach to assess the effects of Sr and Bi interaction in ADC12 Al–Si die casting alloy

• Interactive effect between Bi and Sr has been invesitigated comprehensively.
• Sequence of addition did not affect thermal and microscopical characteristics.
• A new map has been established to assess the final microstructure of castings.

In the present paper, the possible interaction between bismuth and strontium in ADC12 die casting alloy was investigated comprehensively by using in situ thermal analysis technique. The characteristic temperatures including nucleation, minimum and growth temperatures of eutectic Al–Si were also analyzed. The results show that with Bi present in the Al–Si alloy melt the efficiency of Sr in modifying the eutectic Si is reduced. A threshold Sr/Bi ratio of at least 0.5 is required for a fully modified Si structure to form. A new map based on the characteristic temperatures, Sr/Bi ratio and microstructure, was established to assess the microstructure of fully solidified Al–Si castings.