MODELING THERMAL-PROCESSING OF ALUMINUM-ALLOYS

Process modelling methods have been applied to the thermal treatment of aluminium alloys. A model describing the development of microstructure and yield strength during isothermal aging of heat treatable alloys has been developed. This model is illustrated by means of novel 'iso-yield diagrams'. For non-heat-treatable alloys, a similar diagram for recrystallisation of cold rolled material is derived empirically. The isothermal models and diagrams are then applied to processes in which the temperature varies with time, using the concept of the 'kinetic strength' of a thermal cycle. The duration of an isothermal treatment at the peak temperature of the cycle is found; this has the same driving force for kinetic change. Of particular interest is the loss in strength in the heat affected zone of welded joints.