亞共晶型Al-Si合金之初晶相為初晶鋁、共晶矽和富鐵相。未改良之共晶矽以粗針狀形態出現，添加改良劑後可使粗針狀共晶矽纖維化。含鐵量較高之合金易有富鐵相的生成，包含了棒狀和文字型富鐵相。利用等通道轉角擠型(ECAE)改變其初晶相形貌，將影響合金微結構與機械性質。
實驗設計三種不同Sr、Fe含量之合金，使得其微結構有所差異，分別為粗針狀共晶矽、纖維狀共晶矽和棒狀富鐵相。利用ECAE製程改變其初晶相形貌後施予T6熱處理，並結合光學顯微鏡(OM)、電子微探儀(EPMA)、影像分析、穿透式電子顯微鏡(TEM)、導電度計及掃描式電子顯微鏡(SEM)探討ECAE製程改變初晶相形貌對Al-7Si-0.35Mg合金微結構所造成之變化，進而利用微結構之改變來說明其對機械性質所產生之影響。
實驗結果顯示，利用ECAE製程可以有效改變初晶相形貌，對於未改良之粗針狀共晶矽的粒化效果明顯，使其平均深寬比大幅下降；經改良之纖維狀共晶矽，其形態經ECAE製程後之矽顆粒尺寸變化有限。而棒狀富鐵相於ECAE過程中有顯著的斷裂，富鐵相之平均長度也有所減少。其中粗針狀共晶矽的粒化與棒狀富鐵相的斷裂，以及ECAE製程將孔洞密實的優良特性，皆可有效地減少破裂起始點，使得延性有所提升，進而擴展應力應變曲線獲得較高之強度水平，並且可得到較佳之品質指標。

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