MODELING OF HEAT FLOW AND SOLIDIFICATION DURING SPRAY DEPOSITION PROCESS

摘要

The solidification behavior of droplets as well as spray-deposit of Al-4.5 wt percent Cu alloy is simulated by modeling based on heat flow analysis. The model incorporates droplet dynamics and their thermal during atomization process. The resultant spray enthalpy is used to analyze heat flow during solidification of the spray deposit. The effect of process variables like atomization pressure, melt superheat and -nozzle to substrate distance on the solid fraction and enthalpy of the spray is analyzed. The results of modeling are compared with the experimentally determined thermal profile of the spray deposit. The results indicate that the cooling rate for a wide size range of droplets varies from 10~3-10~5 Ks~(-1) in contrast to a slow cooling rate of 1 to 10 Ks~(-1) of the spray deposit. Empirical correlation between cooling rate of the spray deposit and the grain size has been established. It is inferred that cooling rate is not the sole determining factor in controlling grain size of the deposit during spray deposition process.