This paper describes as-cast microstructureof spray formed 3003 alloy deposits produced using alinear nozzle on the spray forming unit at AlcoaTechnical Center and a computational simulation of thethermal condition of the deposit during the deposition process.The general microstructure of a deposit revealsessentially equiaxed grains. The size of the grainsrange from 10 to 40 #mu#m and increases with distancefrom the bottom of the deposit. The size of theconstituent particle Al_12 (Fe, Mn)_3Si increases fromapproximately 2 to 7.5 #mu#m as a function of distancefrom the bottom of the deposit. Based on a pre-established constituent particle size-cooling raterelationship, cooling rate of the deposit decreases fromapproximately 60 to 0.6 deg C/s with distance from thebottom of the deposit. Porosity in the bulk of a depositand base porosity have different origins. Bulk porosityforms as a result of gas entrapment while base porosityforms as a result of substrate chilling and low mass fluxin the leading edge of the spray. The amount of bulkporosity, grain size and constituent particle size ofa deposit decrease as fraction liquid in the sprayarriving at the deposit decreases. Based on the Mnconcentration profiles measured by electron probemicroanalysis, it is evident that the spheroidalparticles in the mushy layer on the top of a depositevolved from the dendrites carried into the deposit, andare the precursors to the equiaxed grains of the deposit.For the deposit and substrate temperature simulation,a coordinate transformation technique is used to accountfor the shape evolution of the deposit during depositionprocess. The first principle equations for the heattransfers are derived and sloved numerically. The modelcalculates the deposit and substrate temperature andpredicts critical process information such assubstrate-side porosity thickness and the thickness ofthe thin liquid layer on top of the deposit in the sprayzone. The numerical results compare favorably with theexperimental data and the model is very useful in helpingprocess design optimization.
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