Abstract
Steady-state directional solidification studies are described for untreated, commercial purity Al-7 Si-0.5 Mg casting alloys. These show that the secondary dendrite arm spacing can be described by the equation, Where tf, is the total solidification time in seconds, and λ is measured in μm. Specimens quenched during solidification are used to follow the coarsening of secondary dendrite arms during solidification. It is shown that coarsening behaviour can be represented adequately by an average coarsening parameter, , in the equation, If the geometrical constant B is assumed to be 33, the value of calculated from the spacing measurements is 22.46 (μm s−1). Factors influencing the value of λ0 are defined and its influence on coarsening behaviour is described.