晶種對於錫鉛合金方向性凝固微結構之影響分析

一般的鑄造過程是不易控制其凝固結構之形態，最多只能改變其晶粒大小，而方向性凝固方法可製造出沿特定方向之柱形枝狀晶的鑄件。本文以錫鉛合金為測試材料，採五種實驗模式來探討不同形狀結構之晶種對於方向性凝固微結構影響。在凝固成長過程中提供一相同成份的多晶晶種，誘發鑄件底部的枝狀晶發育時可沿晶種優選方向成長，消除底部因高溫度梯度形成之細小等軸晶，並獲得較佳之方向性凝固之結構。於實驗中探討不同形狀結構的晶種對其枝狀晶之優選方向控制情形、鑄件晶粒尺寸及對晶體成長的束縛控制的影響及對其溫度梯度、成長速率、主枝狀晶臂間距及二次枝狀晶臂間距之間的影響；並且利用拉伸試驗機對方向性凝固材料進行機械性質測試。

關鍵字

晶種；方向性凝固；錫鉛合金；金相及顯微結構

並列摘要

The morphology of solidification microstructure is difficult to control in a casting process, in which only the grain size can be easily changed. Directional solidification techniques can fabricate the casting of columnar structures growing along one direction. In this work, Sn-Pb alloy is used as the testing material and five different experimental models are utilized to study the shape effects of seed on the directional solidification. In directional solidification experiments, polycrystalline seeds made of the same initial composition as that of the casting are used to bring out the columnar structures growing along the preferred directions of the seeds. This could avoid the formation of small equiaxed dendrites with chaotic orientations at the bottom portion of the casting and obtain the better columnar structures of directional solidification. In this study, the relationship among the different shapes of seed and the preferred growth direction of dendrite, grain size, the constraint of the dendrite growth, temperature gradient, growth rate, primary arm spacing and secondary arm spacing was investigated for these five models.

並列關鍵字

seed ； directional solidification ； Sn-Pb Alloy ； metallography and microstructure

國際替代計量

晶種對於錫鉛合金方向性凝固微結構之影響分析

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