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 calorimeter with slow heating and cooling rate was carried out and supplemented by 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 process, 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)' ternary phase.