本文是以Al-Si-Cu-Mg合金為基礎，分別添加不同含量的Mg、Cu原子以研究此二種元素含量對Al-14.5Si-Cu-Mg合金機械性質的影響。研究中使用光學顯微鏡、電子微探儀(EPMA)、導電度量測(%IACS)、熱差掃描分析(DSC)及電子顯微鏡(SEM)來觀察材料微結構的變化。實驗結果顯示，增加合金中之Mg含量或減少Cu含量(Mg/Cu比增加)，將促使針狀β-Al5FeSi富鐵相轉變成文字型Al8Mg3FeSi6相，若Mg含量高於固溶溫度下之固溶度，將使固溶淬火後基地中Mg、Cu原子比例下降，進而減少人工時效後強化相之析出量及硬度之提升幅度，但拉伸強度及延伸率將因針狀β-Al5FeSi富鐵相數量之減少而有較佳之表現；Cu含量減少雖造成合金T6熱處理後析出強化的效果變差，但拉伸強度及延伸率因針狀β-Al5FeSi富鐵相轉變為文字型Al8Mg3FeSi6相而有所提升。

The effect of Mg、Cu content on mechanical properties of Al-14.5Si- 4.5Cu alloys were investigated. Optical microscopy (OM)， electron probe X-ray microanalyzer (EPMA), electrical conductivity meter (%IACS), differential scanning calorimeter (DSC) and scanning electron microscopy (SEM) were used to monitor the variation of microstructure . The results show that increasing Mg content contribute to transformation of β-Al5FeSi needles into the Al8Mg3FeSi6 compacted Chinese script phase. That Mg content exceeds the solubility under solution temperature lowers the percentage of Mg、Cu atoms dissolving into the Al-matrix during solution treatment. This reduces amounts of precipitates and increasement of hardness after artificial ageing, otherwise, tensile properties perform better due to reduction of the number of β-Al5FeSi needles. Decreasing Cu content reduces the effect of precipitation hardening, but tensile properties are promoted due to the transformation of β-Al5FeSi needles into the Al8Mg3FeSi6 compacted Chinese script phase.

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