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    請使用永久網址來引用或連結此文件: http://ir.lib.ncu.edu.tw/handle/987654321/53901


    題名: 熱處理對車用鋁合金材料熱穩定性與表面性質之影響;Effects of heat treatment on thermal stability and surface properties of aluminum automotive alloys
    作者: 李庚益;Lee,Kent-Yi
    貢獻者: 機械工程研究所
    關鍵詞: 電阻率;Al-12.5Si-4.5Cu-1.0Mg合金;熱處理;熱穩定性;磨耗性質;表面突起;;鋁合金薄膜;濺鍍;Al-12.5Si-4.5Cu-1.0Mg alloy;Heat-treatment;Therm
    日期: 2012-07-30
    上傳時間: 2012-09-11 18:18:54 (UTC+8)
    出版者: 國立中央大學
    摘要: 本研究對Al-12.5Si-4.5Cu-1.0Mg合金施以T6時效處理,以探討時效處理對合金之微結構、與機械性質及高溫熱穩定性之影響,並利用濺鍍沈積法製作Al-Sc合金薄膜,同時施以不同的溫度之熱處理,探討熱處理與Sc元素添加對鋁薄膜晶粒結構、導電特性與表面突起之影響。實驗結果顯示,Al-12.5Si-4.5Cu-1.0Mg合金雖可藉由T6時效處理,析出強化相θ′(Al2Cu相)與λ′(Al5Cu2Mg8Si6相),提高合金的機械強度,但析出相經300℃持溫10小時後會明顯粗化,產生過時效現象,致使時效處理合金之熱穩定性反不如鑄態合金。合金經300℃持溫100小時之熱穩定測試後進行磨耗測試,在低荷重(10N)磨耗時,鑄態合金與時效處理後合金之磨耗量相近,顯示T6熱處理並未對在低荷重的磨耗行為有所影響;但在高荷重(40N)時,由於鑄態合金經300℃持溫處理後之硬度較高,因此耐磨性較T6時效處理後之合金為高。  以濺鍍沈積法製作0~0.4wt%Sc之Al-Sc合金薄膜,同時對薄膜施以200℃、300℃、400℃及500℃之熱處理一小時,並對薄膜晶粒型態、電阻率變化與表面突起特性進行分析。  實驗結果顯示,添加Sc可有效降低薄膜剛沈積時的晶粒尺寸,並可限制晶界的移動,抑制熱處理時晶粒成長與再結晶現象。熱處理可促使Al-Sc薄膜析出Al3Sc相,大幅改善其導電性質,經500℃熱處理後,Al-Sc之電阻率已降低至與純鋁薄膜相近。Sc元素添加可提高鋁薄膜之降伏強度,並減少表面突起數量,且效果隨Sc含量增加而增加;然而經400℃熱處理後,Al-Sc薄膜之突起的尺寸將大幅的增加。This study elucidates the effects of T6 heat treatment on thermal stability and wear behavior of Al-12.5Si-4.5Cu-1.0Mg alloy. The experimental alloys under as-cast and T6 heat-treated conditions were isothermally heat-treated at 300℃ for 100 hours to investigate thermal stability and wear behavior. The results reveal that T6 heat-treatment promoted the precipitation of the λ′ (Al5Cu2Mg8Si6) and θ′ (Al2Cu) phases and the augmentation of hardness of Al-12.5Si-4.5Cu-1.0Mg alloy. However, the coarsening of λ′ and θ′ phases led to a large decrease in hardness following isothermal heat-treatment 10 hours. The thermal stability of the T6 heat-treated alloy was much worse than that of the as-cast alloy. For wear behavior, the as-cast and T6 heat-treated alloys showed the same wear rate with 10N load after isothermal heat-treatment. This indicated the wear rates of Al-12.5Si-4.5Cu-1.0Mg alloys were independent on T6 heat treatment. Under 40N load, the wear resistance of as-cast alloy was superior to that of T6 heat-treated alloy after isothermal heat-treatment.The effects of the heat treatment and Sc contents on grain structure, electrical resistivity and hillocks formation of Al-Sc alloy films were also investigated in this study. Three kinds of Al-x Sc (x = 0, 0.2, 0.4 wt. %) alloy films were prepared via sputtering deposition, subsequently exposed at 200℃, 300℃, 400℃ and 500℃ up to 1 hours.The results revel that the addition of Sc reduced the grain size of the as-deposited films and immobilized the grain boundaries, retarding grain growth and re-crystallization of the films during heat-treatment. Although the as-deposited Al–Sc alloy films showed high resistivity, the former was significantly decreased due to the precipitation of Al3Sc phase during heat-treatment. After 500℃ treatment, the resistivity of Al - Sc alloy films was similar to that of pure Al film. The hillock density dramatically reduced with increasing the Sc concentration in the films. However, average size of the hillocks in Sc containing films clearly increased when heat-treatment temperature was elevated to 400℃.
    顯示於類別:[機械工程研究所] 博碩士論文

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