Al-Zn-Sn phase diagram - Calorimetric study of the isobaric invariants

A systematic study of Al-Zn-Sn ternary alloys by using a Tian-Calvet calori meter with slow heating and cooling rate was carried out and supplemented b y scanning electron microscopic observations. The results have shown that crystallization coupled with dissolution of tin into the alpha(SS)' ternary solid solution on heating is an endothermic pr ocess, while melting coupled with tin expulsion on cooling is an exothermic one. It seems that the thermal effects of phase transition are outweighed by much stronger ones due to a large composition change of the alpha(SS)' t ernary phase.