| Summary: | 碩士 === 中山醫學大學 === 職業安全衛生學系碩士班 === 101 === The traditional fusion welding process was widely used to join the metal matrix composites (MMC). An elevated temperature is required to melt the metal matrix and then to achieve welding. Some hazards formed easily in the welding process such as high temperature, fumes and toxic gases, which harms the welder’s safety. In general, the density of reinforcement is lighter than that of metal matrix, thus, a segregation defect would form when the fusion welding process was applied to join the MMCs. The solid state diffusion bonding process is expected to reduce the bonding temperature and to improve bonding quality of MMCs.
In this study, the solid state diffusion bonding process was used to join Al/(SiC)P and Cu/(SiC)P with an interlayer. The aluminum foil with the thickness of 50um was selected as the interlayer. The major bonding parameters of solid state diffusion bonding, bonding time, bonding temperature and the fraction of reinforcements were investigated. After Al/(SiC)P and Cu/(SiC)P bonded together, the optical microscopy and scanning electron microscopy were conducted to observe the microstructure of bonding interface and to evaluate the fracture mode. The bonding strength of Al/(SiC)P and Cu/(SiC)P was determined using a shear test.
According to the experimental results, the Al/(SiC)P and Cu/(SiC)P can be bonded successfully with an interlayer of aluminum foil by solid diffusion bonding process. The bonding strength increases with the increasing bonding temperature and bonding time. This experimental result implies that higher bonding temperature and extending bonding time promoted the atomic interdiffusion, and the bonding strength is thus enhanced. When the bonding temperature increased to 650°C, the interlayer soften and the flowability increased, larger reinforcements pile up at bonding interface between the Al/(SiC)P and the interlayer. The bonding strength is thus degrading, indicating the bonding temperature should not be closed to the melting point of metal matrix and the interlayer. As increasing reinforcement fraction in the range of 5wt% to 15wt%, the bonding strength increases with the reinforcement fraction, and the highest bonding strength is 80.6 MPa approximately. Adding appropriate fraction of reinforcements is an effective way to improve the bonding strength. However, the bonding strength gradually degrades when an exceeding reinforcement was added. The metal matrix is insufficient to form a sound bond between the reinforcements and the metal matrix. A porosity defect or cracks would be formed between reinforcements and metal matrix resulting in a lower bonding strength.
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