旋壓成型加工對A356(Al-7Si-0.3Mg)鑄造鋁合金微結構與機械性質之影響

The effect of spinning process on microstructure and mechanical properties of cast A356(Al-7Si-0.3Mg) alloy

許釋元(Szu-Yuan Hsu)

指導教授 ： 李勝隆

國立中央大學/工學院/機械工程學系/碩士(2007年)

摘要

A356(Al-7Si-0.3Mg)鑄造鋁合金之微結構中存在樹枝狀初晶鋁、共晶鋁矽與富鐵相。其中，共晶矽與富鐵相屬硬脆相，其大小與型態對A356合金之機械性質有不良影響。除了利用添加元素(改良劑、中和劑)的方式來減輕此兩種相對機械性質的危害外，也可藉由等通道轉角擠型(ECAE)、冷滾軋(cold rolling)等塑性加工的方法來改善。本文將運用旋壓成型技術對A356合金進行加工，探討此加工製程對A356合金微結構與機械性質之影響。
藉由光學顯微鏡(OM)、電子微探儀(EPMA)、熱差掃描分析儀(DSC)、掃描式電子顯微鏡(SEM)、影像分析及導電度計(%IACS)等儀器對經旋壓成型加工後之A356合金微結構做一詳盡之觀察與分析；並結合硬度試驗、拉伸試驗及品質指標來評估其機械性質上之差異。
結果顯示，旋壓成型加工對已添加Sr改良之共晶矽的型態無顯著之影響，主要在改變共晶矽之分布，且能有效打斷棒狀β- FeSiAl5富鐵相。旋壓成型加工雖對熱處理後之導電度、硬度與抗拉強度影響不大，但能有效改善延伸率。經加工後，延伸率由8.8%提升至11.7%，而品質指標(Quality Index)也從418 MPa上升到432 MPa，顯示經旋壓成型後，A356合金之拉伸性質獲得明顯改善。

關鍵字

拉伸性質 ； 富鐵相 ； A356合金 ； 旋壓成型加工

並列摘要

A356 alloy contained two kinds of brittle phases, i.e. eutectic silicon and Fe-bearing phases. The morphology of brittle phases were detrimental to the mechanical properties. Among the various methods available to reduce the harmful effects of brittle phases, modification by using equal channel angular pressing and cold rolling were practiced. In this study, the effect of spinning process on microstructure and mechanical properties of A356 alloy were investigated.
Microstructural features were elucidated by optical microscopy, electron probe X-ray microanalysis, scanning electron microscopy, image analysis, measurement of electrical conductivity and differential scanning calorimetry.The microstructure was correlated with Rockwell
hardness and tensile testing.
The microstructure of A356 alloy was deformed after spinning, the initial coarse dendritic structure was broken
into an elongated structure.Eutectic silicon was more homogeneously distributed within the deformed regions and Fe-bearing phases were broken into fine pieces.Although
the electrical conductivity, hardness and ultimate tensile strength of T6 treated A356 alloy were no influence after
spinning, the tensile properties were improved.

並列關鍵字

Fe-bearing phases ； Tensile properties ； A356 alloy ； Spinning

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