Simultaneous hot isostatic pressing and solution annealing of aluminum cast alloys followed by instantaneous aging at elevated temperatures

Age-hardenable aluminum - silicon - magnesium cast alloys are widely applied in automotive and aircraft industries. Hot isostatic pressing is a common method to increase the materials fatigue resistance by reducing the inner porosity of aluminum cast materials. In the presently followed industrial production route hot isostatic pressing is performed preceding the standard heat treatment consisting of solution annealing and aging. In previous work Hafenstein et. al. demonstrated the possibility to achieve an oversaturated condition with a sufficient amount of magnesium and silicon atoms dissolved in the aluminum matrix by performing rapid temperature changes in advanced hot isostatic presses. Hence, it becomes possible to combine hot isostatic pressing and solution annealing within a single process step and to perform aging at elevated temperatures immediately after hot isostatic pressing without the necessity of separate solution annealing. The present study evidences that the design of a fully integrated process which comprises not only hot isostatic pressing and solution annealing but also aging at elevated temperatures is possible thereby shortening further the overall processing time. It is shown that the benefit with respect to strength in such a combined process is due to the shortening of the time at room temperature between solution annealing and aging at elevated temperatures.