A356鋁合金為一可熱處理型鑄造鋁合金，因其具有良好之流動性、磨耗性與焊接性等優點，已被廣泛應用於航空與汽車工業，然而A356鋁合金中的鐵元素，易與鋁形成β-Al_5 FeSi針狀富鐵相，造成合金機械性質的傷害。本研究藉由微結構觀察與機械性質試驗，探討不同含量的鐵與錳元素對A356鑄鋁合金(Al-7Si-0.3Mg)機械性質之影響。分別以光學顯微鏡(OM)、電子微探儀(EPMA)及掃描式電子顯微鏡(SEM)，觀察合金中的微結構變化與破裂斷面。 結果顯示合金中的共晶矽含量與形態，並未因鐵與錳的添加而有差異。而針狀β-Al_5 FeSi富鐵相隨鐵含量的增加而增多且粗大化，導致合金機械性質、尤其是延性的顯著損害。另外錳的添加，可使針狀β-Al_5 FeSi富鐵相轉變為多邊型α-Al15(Fe,Mn)3Si2富鐵相，可有效改善合金機械性質、提升延性。此外，合金中鐵含量愈高，所需添加之錳含量亦須提高，才能達到改善效果。A356 aluminum alloy is a heat treatment type cast aluminum alloy, with excellent casting characteristics、resistance to corrosion and good weldability, have been widely used in aircraft and automotive industry.Iron is the most common and harmful impurity in A356 aluminium alloys forming acicular form of β-Al5FeSi iron intermetallic phase, which is detrimental to the mechanical properties. In this study, the effect of Mn and Fe on mechanical properties of A356 alloys by used microstructure observed(OM、EPMA and SEM) and mechanical test. Addition of Fe and Mn elements has no obviously influence on the type and amount of eutectic silicon in A356 alloy. Increasement of Fe content in A356 alloy, which amount and size increase with increasing Fe content. And lead to the decline of mechanical properties. Addition of Mn change the morphology of β-Al5FeSi acicular iron intermetallic phase to α-Al15(Fe,Mn)3Si12 polyhedral form leading to significant improvement in mechanical properties.
