| Summary: | 碩士 === 國立中山大學 === 材料與光電科學學系研究所 === 102 === Directional solidification technique applied to investigate the dendrite alloy segregation and the phase identification in multiple phases co-precipitation. Because the large size dendrite could form in directional solidification which would provide large scale to investigate the dendrite segregation from dendrite center region to edge region. For the eutectic type alloys, several phases formed together and have the difficulty to identify these fine phases. These alloys could solidify under slower directional solidification condition and form larger phase.
A356 aluminum alloy and add 1 wt.%Mn alloy were applied in this study. The influence of thermal gradient, extruding rate and chemical composition to microstructure were investigated. In A356 aluminum alloy and it add 1wt.% Mn we found the Al dendrite is larger than nature cooling then it is good to carry out quantitative analysis, we also can find the Al dendrite grow paralleled with heat in A356 but not in A356 with 1wt.% Mn, and the precipitate will convert to fibrous from plates when the extruding rate reduced. When A356 alloy addition 1 wt.% Mn the Al5FeSi IMC would convert to Al15(Fe,Mn)3Si2.
We also take Al-Si and Al-Si-Cu eutectic system, due to the current temperature parameter, the microstructure is not as expected. Because the
lower thermal gradient caused the lower cooling rate, and generated ageing behavior. Thus the change of extruding rate is not affecting the microstructure.
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