MODELLING OF DISPERSOID AND CONSTITUENT PARTICLE EVOLUTION IN 3XXX ALLOYS

摘要

A kinetic model is described for dispersoid and constituent particle evolution during preheating of 3XXX alloys. Dispersoid modelling combines the parallel processes of nucleation, growth and coarsening, resulting in evolution equations for number density and volume fraction of dispersoid. Constituent modelling combines the parallel processes of growth (or dissolution) and transformation from Al_6[Fe,Mn] to Al_(12)[Fe,Mn]3Si phases, resulting in evolution equations for volume fractions of these phases, as well as Mg_2Si. The evolution equations for dispersoids and constituents are coupled to each other through the matrix concentrations of manganese and silicon. Adjustable parameters relate to nucleation kinetics, interfacial energy and equilibrium solvi. The model is fit to conductivity data, dispersoid size measurements and constituent characterization. The data contain variations in solidification rate, alloy composition and thermal history. The resulting model can be used to predict effects of process excursions, or to search for new combinations of alloy composition and thermal practice, on the basis of physical principles and prior data.