Quench rate and aging effects in aluminum-zinc-magnesium-copper aluminum alloys

This work examines the effect of quench rate on the homogeneously and heterogeneously distributed precipitation occurring in Al-Zn-Mg-Cu commercial alloys, 7075 and 7050. Techniques used included hardness, conductivity and a differential scanning calorimetry (DSC) to understand and quantify precipitation in commercial 7075 and 7050 aluminum alloys. The use of the Jominy End Quench test to determine quench factors for the prediction of properties was developed. In addition, the use of Jominy End Quench data to develop Time-Temperature-Property curves (C-Curves) was demonstrated. The effect of quench rate on the width of precipitate free zone was examined. It was determined that at quench rates greater then 60°C/sec., vacancy depletion dominated. At slower quench rates, it was determined that solute depletion dominated the precipitate free zone. The critical vacancy concentration for precipitation was established as a function of quench rate --Abstract, page ii