摘要
6066鋁合金具有中高強度、抗腐蝕性佳、成形性佳以及可焊性佳等優點，因此廣泛運用在運輸、建築工業上。儘管6066鋁合金具有以上優點，但是其拉伸性質穩定性差。本實驗於一般固溶熱處理前施以一段高溫熱處理，探討改善第二相粗大問題是否能夠提高其拉伸性質之穩定性。另外，利用韋伯分佈評估6066鋁合金之降伏強度與總延伸率之可靠度。

本研究中，6066鋁合金分成兩種熱處理方式。一種為一般固溶熱處理，固溶溫度為530 oC，時間2小時，之後進行T6處理，溫度為175 oC，時間為峰值時效6小時(稱為530-N6材)。另一種為過高溫固溶熱處理，過高溫固溶溫度為 550 oC至580 oC，時間1小時，接著進行一般固溶熱處理，530 oC，時間2小時，之後進行T6處理，溫度為175 oC，時間為亞時效6小時與峰值時效9小時。

實驗結果顯示，當過高溫固溶處理溫度為560 oC左右時可發現Mg2Si相發生分解。除此之外，過高溫固溶處理亦會改變Al12(FeMnCu)3Si相形貌由碎片狀轉變為團狀。在拉伸性質部分，Q相(Al5Cu2Mg8Si6)熔融凝固後造成過高溫固溶處理T6材之拉伸強度下降。儘管過高溫固溶處理後之拉伸強度不及一般固溶峰值時效材，但是其韌性較佳，由其是過高溫固溶處理亞時效材。在韋伯分佈部分，過高溫固溶亞處理時效材之YS可靠度較530-N6材好，且位置參數與530-N6材相近。韋伯分佈數據亦顯示，過高溫固溶處理亞時效材能夠改善6066鋁合金降伏強度、總延伸率之數據分佈集中性。由實驗結果得知，過高溫固溶亞時效材之6066鋁合金拉伸數據分佈集中，十分適合應用在需要高韌性條件之汽車與建築工業上。

6066 aluminum alloy can be used in a variety of applications including automotive industries and architecture due to its attractive properties, such as medium strength, good corrosion resistance, formability and weldability. However, it has a huge fluctuation on tensile properties. In order to assess reliability of tensile properties, specimens were treated with overheated solution treatment to make coarse phases homogenously into microstructure, then using Weibull analysis assess reliability of yield strength and total elongation.

In this thesis, some specimens of 6066 aluminum alloy were treated with normal solution treatment at 530 oC/2h prior to water quenching and aging at 175 oC/6h. The others were treated with heating at 550 oC to 580 oC/1 h followed by solution treatment at 530 oC for 2h prior to water quenching and aging at 175 oC/6h or 9h. We discuss tensile tests and reliability of both heat treatments on 6066 aluminum alloy.

The results showed that overheated solution treatment plays an important role in the decrease of Mg2Si size when samples were heated at 560 oC. Furthermore, morphology of Al12(FeMnCu)3Si phase was changed from script-like features to rounded features. This melted Q phase (Al5Cu2Mg8Si6) caused tensile strength of samples lower than normal heat treatment followed by peakaging. Although Yield strength of overheated solution treatment prior to peakaging or underaging was less than normal solution treatment prior to peakaging, material toughness was much better than normal one. With respect to Weibull analysis, overheated solution treatment prior to underaging could easily predict stress that a sample begins to deform plastically. Location parameter of this treatment is as same as normal solution treatment prior to peaking. The Weibull analysis results also showed that overheated solution treatment prior to underaging could improve reliability of yield strength and total elongation Weibull distribution function. Totally, normal solution treatment can be substituted for overheated solution treatment prior underaging due to its tensile reliability and toughness. Therefore, this heat treatment is suitable for 6066 alloy on high toughness conditions especially for automobile and architecture.

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