- 學位論文
以鋁接合鋁基碳化矽複合材料之研究
Study on diffusion bonding of aluminum metal matrix composite reinforced with silicon carbide using an aluminum interlayer
摘要
近年來工業迅速發展，鋁基碳化矽複合材料廣泛應用於汽車、航太工業與醫療產業等，為擴大鋁基碳化矽複合材料之用途，鋁基碳化矽複合材料之接合製程以熔融焊接為其主要方法，但熔融焊接過程中易伴隨輻射線、強光、金屬燻煙、高溫、有害氣體且具有感電之潛在危害，容易導致勞工產生白內障、皮膚癌、肺部病變及感電致死等職業災害，且因金屬基複合材料之強化材與基材間比重不同，熔融焊接容易使焊件中強化材產生偏析、雜質的混入，致使接合處出現氣泡與孔洞等缺陷，進而影響焊件之品質，故開發低危害與高性能之接合技術應用於鋁基碳化矽複合材料，實為必行之趨勢。 本研究藉由工程改善方式降低製程溫度、隔離高溫、高輻射等危害以提高鋁基碳化矽複合材料之作業環境安全及衛生條件，並克服熔融焊接容易產生之不良影響。本實驗主要以熱壓製程，將鋁粉末與碳化矽顆粒先行混合後燒結成母材，選用鋁金屬箔片作為接合層材料，藉由熱壓法在低於基材熔點之製程溫度下進行接合，探討以擴散原理進行接合之品質及接合形態。製程參數選用之製程溫度為350℃- 600℃、碳化矽強化材含量為5wt%-30wt%、燒結之持溫時間為10min-90min。研究重點包括各參數接合試片之巨觀與微觀結構差異、破斷面觀察、成份分析、接合後緻密度與剪切強度等。 實驗結果顯示當製程溫度提升，可有效促進鋁基材與鋁接合層材料原子間交互擴散，有助於提升鋁基碳化矽複合材料接合之緻密度及剪切強度；碳化矽強化材含量的提升有助於提升剪切強度，當碳化矽強化材含量持續增加時，鋁基材無形成有效之鍵結，故其強化效果隨之下降；持溫時間增加時，接合試片之緻密度與剪切強度隨之增加，但持溫時間過長時，剪切強度呈現下降的趨勢，主要原因為鋁基材產生晶粒之粗大化，致使剪切強度下降。當製程溫度600℃、碳化矽強化材含量25wt%、持溫時間30min，鋁基碳化矽複合材料之剪切強度達最高值104.1MPa，且破斷面主要出現為母材，說明接合區之強度高於母材強度，顯示鋁接合層材料與鋁基複合材料具良好的接合強度。綜整實驗結果得知，熱壓接合製程可提供鋁基碳化矽複合材料良好接合品質，並可降低傳統熔焊製程之危害因子，提高職場作業安全。
並列摘要
The metal matrix composite (MMC) has been used in automobile, aerospace and medical industrial. The welding process was a main scheme to fabricate the complex parts due to the machinability of the MMC was limited to their high hardness. However, the density of metal matrix is lighter than those of reinforcement, a separation occurs when metal matrix was molten and the defect of segregation would be form. This defect would degrade the welding quality of the MMC. Furthermore, the traditional arc fusion welding process has several potential hazardous factors, high temperature, fume, toxic gases and radiations to affect the occupational safety and welder’s health. In this study, a solid diffusion bonding process, hot pressing method was thus employed to improve the bonding quality of MMCs and to reduce the hazardous factors of bonding process. An aluminum reinforced with silicon carbide (SiC) particles was used as based metals, which were fabricated by powder metallurgy method. To increase the bondability of Al/SiC MMCs, an aluminum foil with a thickness of 50μm was selected as a bonding layer. The Al/SiC MMCs joins to each other with an aluminum foil bonding layer at an air atmosphere. The effects of main processing parameters, bonding temperature, bonding time and the fraction of reinforcement on the bonding quality were investigated. The bonding strength of MMCs was evaluated using a shear test, the observation and compositions identified on the fracture surfaces were using scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS). The Al/SiC MMCs bonded successfully with the Al bonding layer and both the bonding strength and density ratio were improved with increasing the bonding temperature. An elevated bonding temperature enhances the atomic interdiffusion between the Al base metal and the Al bonding foil. Increasing the fractional SiC reinforcement of base metal, the bonding strength is improved. However, the fraction of SiC reinforcement in base metal increases to 30wt%, SiC particles clusters at bonding interface to obstruct the Al atomic interdiffusion, and the bonding strength thus decreases significantly. Although extending the bonding time provides a high thermal input which enhances the Al atomic interdiffusion, and to improve the bonding quality, but the higher thermal input causes the grain growth and grain coarse on Al matrix leading to degrade the bonding quality. In the work, the highest bonding strength was 104.1 MPa for Al/SiC MMC with 25wt% reinforcement bonded at 600°C for 30min. This experimental result not only demonstrates the high bonding quality for Al/SiC MMC bonding to each other, but also this solid diffusion bonding process could reduce the procession hazards comparing the conventional fusion arc welding procession.