汽車車體骨架用6000系鋁合金低溫時效與擠型條件之研究

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题名:	汽車車體骨架用6000系鋁合金低溫時效與擠型條件之研究
作者:	高國瑜;Guo-Yu Gou
贡献者:	機械工程研究所
关键词:	擠製;低溫時效;熱變形抵抗;鋁合金;Al-Mg-Si;6000;EXTRUSION;aging
日期:	2000-06-28
上传时间:	2009-09-21 11:32:53 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	本論文針對Al-0.72Mg-0.42Si鋁合金，首先選取不同預時效條件，探討預時效對擠型用Al-Mg-Si合金高溫時效析出硬化之影響。其次改變合金成份及擠型參數，探討其對材料之熱變形抵抗影響。實驗方法分為兩部份，第一部份是使用微差掃描熱分析(DSC)及電阻量測來研究合金的時效析出舉動，並配合穿透式電子顯微鏡(TEM)觀察合金析出強化相的分布情形，並以拉伸試驗(Tensile Test)來量測合金降伏強度及最大抗拉強度的高低。解析6063合金在經過預時效及高溫時效之後，強度不佳的原因。並期望能提出最佳的熱處理製程，使得材料在經過預時效及高溫時效後，能達到最佳的硬化能力。第二部份是利用Gleeble壓縮試驗及擠型最大壓力配合微差掃描熱分析(DSC)及穿透式電子顯微鏡觀察（TEM），評估合金元素、擠製溫度對熱變形抵抗的影響。由實驗結果可知，6063合金經固溶處理．淬水，於40∼70℃進行長時間預時效時，基地內會有G.P.Zones(Π)及β′的核形成，其並不影響高溫人工時效時β′強化相的析出。並且，G.P.Zones(Π)的密度會因為預時效溫度的提升或時間的增長而增加。但在30℃下預時效時，基地內會產生G.P.Zones(I)，其會抑制高溫人工時效時β′強化相的析出，對材料強度有負面影響。另一方面，擠製溫度越高則材料的熱變形抵抗越小；添加Mg、Si、Fe等合金元素越多，則材料之熱變形抵抗越大。其中，以添加過量Mg的合金在擠製時的最大擠製壓力最高。相反的，添加微量的Mn可促進材料中β-AlFeSi相變態為α-AlFeSi相，降低合金之熱變形抵抗。 First, precipitation behaviors of AA6063 (Al-0.72Mg-0.42Si) during pre-aging and the age-hardening after artificial aging were analyzed by using differential scanning calorimetry (DSC) and by measuring the resistivity, and confirmed by microstructure observation using transmission electron microscope (TEM). The tensile test was performed to obtain the mechanical properties of the alloys. The results indicate that G.P.zones (II) of 6063 alloy is formed at 40 ~ 70℃ of pre-aging temperature and has no influence on age-harding after artificial aging, even in a long period. Increasing either the temperature or holding period of pre-aging will significantly increase the strength after artificial aging. Second, the hot defotmation of AA6063 Al alloys has been related to chemical compositions, and the extrusion parameters including reheating temperature, container temperature, and extrusion rate. The extrudability was investigated using Gleeble compression test and the results were in good agreement with the actual extrusion test. The precipitation properties during extrusion were also measured using differential scanning calorimetry (DSC), and the microstructure observations were performed using and transmission electrion microscope (TEM). The results indicate that higher extrusion temperature can obtain better extrudability. However, matreials with excess Mg, Si, and Fe elements will reduce extrudability. And the maximum extrusion pressure in Mg-excess material was greater than that in Si-excess material. In another hand, a small addition of Mn sifnificantly accelerates the homogenising process (transfoemation of the brittle platelike β-AlFeSi phase to the more rounded α-AlFeSi phase) which results in superior hot formabilitu and ductility.
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