Influence of different homogenization heat treatments on the microstructure and hot flow stress of the aluminum alloy AA6082

Abstract

Proper design of the homogenization heat treatment of 6000 series Al wrought alloys is crucial for processes such as hot rolling and extrusion. Important aspects are the precipitation and growth of dispersoids and the dissolution and re-precipitation of Mg-Si-precipitates. Studying these processes is laborious and experimentally demanding, limiting the feasibility of systematic study of variations in the homogenization regime. We conducted in situ differential scanning calorimetry (DSC) experiments of homogenization of AA6082 at different soak temperatures and cooling rates. The resultant heating and cooling curves were interpreted to obtain information on dispersoid number density and Mg-Si-phase dissolution and re-precipitation. Microstructural differences have been evaluated by scanning electron microscopy analysis. The results elucidate the complex relations between dissolution of primary Mg-Si-precipitates, dispersoid precipitation and growth, Mg-Si-re-precipitation, and hot forming behavior while reducing experimental effort compared to semi-industrial furnace trials. Overall, the homogenization soak temperature had the largest influence on these microstructural phenomena while differences due to the cooling rate were less pronounced in an industrially relevant range. In conclusion, in situ DSC can be used as a tool for rapid and inexpensive investigation of homogenization parameters • In-depth analysis of heating and cooling DSC curves. • Use of industry-relevant heating rates and homogenization soak temperatures/times. • Experimental effort is reduced compared to furnace trials. • Advanced SEM characterization of constituents, dispersoids, and Mg-Si-phases. • Microstructure after homogenization is discussed with regards to hot flow stress.