EFFECTS OF SOLIDIFICATION VARIABLES ON INGOT STRUCTURE

Abstract : Results are summarized of experimental and analytical studies of solutionizing aluminum alloys containing a non-equilibrium second phase. Dendrite arm spacing, solution treatment temperature, and alloy content are the important processing variables determining time required to eliminate second phase. At a typical temperature used to solutionize 'premium quality' aluminum-4.5 per cent copper alloy castings, required time for essentially complete elimination of second phase is 25 times the original solidification time. Experiments were conducted on dendritic and non-dendritic solidification of aluminum-copper alloys and of a magnesium-zinc alloy. Grain diameter in the non-dendritic melts was found to depend on solidification time in quantitatively the same way as dendrite arm spacing in the dendritic melts.