An Investigation of Improperly Quenched (Soft) Aluminum Plate.

A program was conducted to evaluate the effects on mechanical properties of a slack slow quench on one side of a plate following the solution heat-treatment of high strength aluminum alloys. Seven thick plates, ranging from 1-14 to 5-12 inches thick, were tested for their tensile properties. Hardness and electrical conductivity readings were taken on all of the specimens to ascertain whether or not recommended limits for these two indicators can accurately identify sub-strength soft material. One 5-12 inch thick plate of 2124-T851 was given a more extensive mechanical property evaluation than the others. On this plate it was observed that the tensile, compressions, bearing, strength of elemental joints, and notched fatigue strength at moderately high stress showed a significant reduction in properties. Smooth fatigue, crack growth resistance, fatigue crack growth, and corrosion resistance were not affected by the slack quench. Other plates of 7000- and 2000-series alloys were also evaluated. A wide range of conductivity and hardness values were correlated with mechanical properties. One 1-14 inch plate of 7075-T651 had low tensile properties on both sides, the cause of which is unknown. Within a given plate, hardness and conductivity measurements did correlate reasonably well with strength variations. Plate-to-plate correlations were less valid. Author