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3652 |
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Thursday, May 22, 2014, Hall H2 4:40 PM Modeling & Simulation 2 |
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Phase selection during rapid solidification of plasma sprayed alumina splats on an alumina substrate |
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Chang-Jiu Li* / Xi'an Jiaotong University, P.R. China Er-Juan Yang / State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, China Jun-Jun Xin/ Xi'an Jiaotong University, China Guo-Xiang Wang/ Xi'an Jiaotong University, China Guan-Jun Yang/ State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, China |
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This paper provides a mathematical description of nucleation, phase selection, and rapid solidification in a plasma-sprayed alumina splat on an alumina substrate at a high initial temperature. The effect of the substrate initial temperature on the phase selection of alumina splat due to varied catalytic effect of the alumina substrate on crystalline nucleation of various phases was examined. The model describes only the thermal problem after complete spreading of the impinging particle on the substrate. It is assumed that heat transfer occurs exclusively in one direction, perpendicular to the substrate surface. The model includes under-cooling phenomenon, heterogeneous nucleation and crystal growth kinetics. The model predicts that crystalline structure of alumina splats changes from ±-Al2O3 crystalline through quasi-stable ³-Al2O3 crystalline to amorphous phase with the change of the substrate temperature from high (900) to low (300), which agrees well with the experimental results. The paper also investigates the detailed solidification characteristics of metastable g phase and stable a phase under the intermediate and high initial substrate temperatures. |