| Summary: | 碩士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 91 === A356 aluminum alloy are being widely applied in the industry due to the material’s good castability and mechanical properties. However, the mechanical properties can be degraded by the formation of porosity. Grain refinement is considered as a required treatment to upgrade the mechanical properties of the alloy. In this study, we investigate the effect of grain refinement on the distribution of porosity in a permanent mold casting.
SKD61 permanent mold was used to cast 25Φ×150L㎜ sample. In the experiment, the mold temperature and the hydrogen content in the melt were fixed. Thermal measurements were used to obtain the thermal variables in the casting.
Grain refiner was found to reduce the porosity of A356 casting from the result of experiment. In the grain-refined condition, rp varies with Pg, grain size, and local solidification time. Because of the smaller grain size in the grain-refined condition, rp was found smaller than that in the non grain-refined condition.
The result of the experiment shows that there is a small re is smaller in the grain-refined condition. However, the reduced of porosity content is mainly due to the decrease of rp in the grain-refined condition. In this study, the prediction of porosity content by theoretical analysis generally agrees with the experiment.
|
|---|
