Tests concerning EN AC 48000 (AlSi12CuNiMg) alloy phase transition covered (ATD) thermal analysis and (DSC) differential scanning
calorimetry specifying characteristic temperatures and enthalpy of transformations. ATD thermal analysis shows that during cooling there
exist: pre-eutectic crystallization effect of Al9Fe2Si phase, double eutectic and crystallization α(Al)+β(Si) and multi-component eutectic
crystallization. During heating, DSC curve showed endothermic effect connected with melting of the eutectic α(Al)+β(Si) and phases:
Al2Cu, Al3Ni, Mg2Si and Al9Fe2Si being its components. The enthalpy of this transformation constitutes approx. +392 J g-1
. During
freezing of the alloy, DSC curve showed two exothermal reactions. One is most likely connected with crystallization of Al9Fe2Si phase
and the second one comes from freezing of the eutectic α(Al)+β(Si). The enthalpy of this transformation constitutes approx. –340 J g-1
.
Calorimetric test was accompanied by structural test (SEM) conducted with the use of optical microscope Reichert and scanning
microscope Hitachi S-4200. There occurred solution's dendrites α(Al), eutectic silicon crystal (β) and two types of eutectic solution: double
eutectic α(Al)+β(Si) and multi-component eutectic α+AlSiCuNiMg+β.