2002 Fiscal Year Final Research Report Summary
Rapid Solidification of Supercooling Binary Molten Metal Droplets
| Project/Area Number |
12650735
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Metal making engineering
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| Research Institution | KYUSHU UNIVERSITY |
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Principal Investigator |
FUKAI Jun Department of chemical Engineering, Professor, 工学研究院, 教授 (20189905)
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| Project Period (FY) |
2000 – 2002
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| Keywords | rapid solidification / molten metal / impact / binary / supercooling / spray forming / numerical |
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| Research Abstract |
A mathematical model describing the deformation and solidification behavior of molten metal droplets impinging on substrates is presented. The mathematical model is numerically solved using a finite element method. In the experiment, a molten tin droplet (2.2-4.3 mm diameter) impacts copper, stainless steel and glass substrates at various impact velocities (1.4-4.0 m/s). The values of the heat transfer coefficient at the droplet/substrate interface are evaluated by comparing the calculated splat diameters to the experimental ones. The estimated values are within the previously reported ranges. The model almost predicts the Weber number dependence of the experimental splat diameters. The time variations of the numerical splat diameters also agree with the experimental results. The simulation reveals that the frozen layer at the splat edge, rather than at the center region, affects the deceleration of the droplet spreading. The effect of the solidification on the splat diameter is explained from the freezing rate at the splat edge.
One-dimensional heat and mass transfer problems are numerically solved to predict microstructure development in alloy splats in rapid solidification. The model accounts for nonequilibrium solidification. The dendrite tip radius is estimated using an interface stability analysis. Model predictions are compared with microstructures of Sn-5wt.%Pb splats produced by depositing mono-size droplets on a Sn substrate. The droplet temperature at impact is controlled by adjusting the flight distance to the substrate. The deposit microstructures primarily match those predicted by the numerical simulation, although not perfectly. The discrepancies between the model predictions and the experimental observation are discussed.
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