本研究是針對A390鋁合金（Al-17%Si-4.5%Cu-0.55%Mg)之矽形態控制
做一深入探討。研究方法上，擬探究磷（P) 和鍶（Sr)分別對初晶矽和共
晶矽顯微組織的影響。而磷和鍶二元素之交互作用亦將作一分析。同時，
亦考量鑄件之凝固冷卻速率對於A390鋁合金顯微組織之影響。此外，矽形
態與相關機械性質，如硬度、耐磨耗性及抗拉強度等之關係亦將做一探討
。 實驗結果顯示磷會細化初晶矽，但對共晶矽則無影響。鍶會將
初晶矽形態從塊狀改變為樹枝狀組織，且亦能調質共晶矽組織，使其從針
狀或片狀細化為纖維狀組織。磷與鍶因具有中和作用，故其共同調質的組
織，會因何者殘存的含量較多，而偏向其組織。 當冷卻速率愈快時，
A390鋁合金的組織愈均勻，其初晶矽相愈細小，且共晶矽相調質效果愈佳
。經磷調質過後且產生均勻分佈的初晶矽之A390鋁合金，其耐磨耗性較佳
。A390鋁合金經鍶調質過後，若其共晶矽細化為纖維狀時，抗拉強度會較
高，但當初晶矽呈現樹枝狀或星狀，抗拉強度會降低。 在組織均勻的
情況下，0.02%Sr調質的A390鋁合金，其耐磨耗性最佳。磷調質的硬度、
耐磨耗性及抗拉強度等機械性質均比鍶調質和磷與鍶共同調質的硬度、耐
磨耗性及抗拉強度等機械性質好。所以，如果要同時擁有高抗拉強度與較
佳的耐磨耗性，調質A390鋁合金的初晶矽比調質A390鋁合金的共晶矽較佳
。關鍵詞 : A390，矽形態，機械性質

The purpose of this research is to manipulate the silicon in
A390 aluminum alloy.The effects of phosphorus or/and strontium
to the primary silicon and eutectic silicon are discussed. The
effects of cooling rate to the microstructure of A390 aluminum
alloy and the relationships between silicon morphology and
mechanical properties, i.e. tensile strength, hardness and wear
resistance, are under consideration.The results reveal that
phosphorus yields a better refinement of the primary silicon but
does not modify the eutectic silicon. Strontium changes the
morphology of primary silicon from the blocky crystallographic
form to a dendritic ones. It also modifies the eutectic silicon
to a very fine structure. Because phosphorus consumes strontium,
the structure which are modified by both phosphorus and
strontium is dicided by the resident volume.When the cooling
rate gets more rapid, the organization of A390 aluminum alloy
will become more uniform, the primary silicon finer, the
modification effect of eutectic silicon greater. A390 aluminum
alloy, modified by phosphorus to produce uniform primary
silicon, will have better wear resistance. When A390 aluminum
alloy is modified by strontium and its eutectic silicon is fined
to fiber, the tensile strength will be stronger; nevertheless
when its primary silicon becomes dendritic or star-shaped, the
tensile strength will be lower.In the well-mixed state, A390
aluminum alloy modified by 0.02%Sr has the optimum wear
resistance. The mechanical propertis of phosphorus treated
alloys are better than those of strontium treated alloys or
phosphorus-and-strontium treated alloys. If both the strong
tensile strengh and great wear resistance are considered,
modifying primary silicon in A390 aluminum alloy is better than
modifying eutectic one.keyword : A390, silicon morphology,
mechanical properties
The purpose of this research is to manipulate the silicon in