On the quench sensitivity of 7010 aluminum alloy forgings in the overaged condition

The quench sensitivity of an overaged 7010 alloy forging was characterized by tensile and Vickers hardness tests, as well as scanning electron microscopy. Longitudinal tensile specimens, excised from a rectilinear open die forging were cooled from the solution treatment temperature following thirty-two different cooling paths including interrupted and delayed quenches. SEM analysis of the microstructure showed that quench precipitates were (i) Al2CuMg (S) which nucleated heterogeneously on grain boundaries and (ii) Mg(Zn,Cu,Al)2 (η) on grain boundaries, dispersoid bands, subgrain boundaries as well as in the aluminum matrix. The quench sensitivity of the alloy׳s yield strength and Vickers hardness was modeled simultaneously by quadruple-C curves, using an improved methodology for Quench Factor Analysis. The four C-curves used in the model represented loss of solute by (i) precipitation of S on grain boundaries, and precipitation of η (ii) on grain boundaries and dispersoid bands, (iii) on subgrain boundaries and (iv) in the matrix. The model yielded coefficient of determination (R2) values of 0.967 and 0.974 for yield strength and Vickers hardness, respectively. The model and the implications of the results are discussed in this paper.