DIFFERENTIAL SCANNING CALORIMETRIC ANALYSIS FOR 7075-ALUMINUM-ALLOY

Differential scanning calorimetry has been used to follow the solid st age reaction accompanying heating and to characterize matrix precipita tes in solution treated, solutions treated and 90% cold rolled, T-6, r etrogression and reaging and T-85 tempers of 7075 alloy. The peak temp erature of dissolution peaks has been used to compare the relative sta bility of pre-existing precipitates in different tempers. Enthalpy is directly proportional to volume fractions of dissolving precipitates. The relative stability of pre-existing precipitates in Tg(6) T-85 RRA tempers is related primarily to activation energy. The pre-existing pr ecipitates are most stable in RRA temper, intermediately stable in T-8 5, and least stable in T-6 temper.