OPTIMIZATION OF HOMOGENIZING MODE FOR ALUMINUM ALLOY AA7075 USING CALORIMETRIC AND MICROSTRUCTURAL STUDIES

Modes of heat treatment are developed for homogenizing cast structure of commercial aluminum alloy AA7075 with the aim of improving its process ductility. The temperature is optimized with the help of differential scanning calorimetry. Computations and studies of microstructure are used to optimize the hold time for the given grain size from the standpoint of minimizing the consequences of dendritic segregation over grain bodies and of dissolution of particles of second phase. A two-stage cycle of homogenizing (470 degrees C, 18 h + 490 degrees C, 7 h) is suggested for cast alloy AA7075 with the initial mean grain size of 200 mu m in cast condition.