Microstructure and Properties of Al/K9 Glass Brazed Joints Based on AlSi12 Brazing Material
The brazing of Al and K9 glass was achieved by using A1Si12 filler.The effect of temperature on microstructure and properties of Al/AlSi12/K9 glass was characterized by scanning electron microscope(SEM),energy dispersive spectrometer(EDS)and universal material testing machine.The results show that a homogeneous Al/AlSi12/K9 brazed joint can be obtained at 610 ℃ within 20 min.Heterogeneous melting and spreading of filler will cause cracks and pores in the brazing seam with the low temperature,while the ablation of substrate occurs at the high brazing temperature making the poor-quality joint.The hypoeutectic liquid phase is produced due to the dissolving of Al by molten filler.With the decrease in temperature,α-Al and primary Si precipitates at the brazing seam,and a metallurgical bonding is formed at the boundary of K9 glass with the interface structure:Al/α-Al+Sip+AlSi eutectic phase/Al2O3+Si/K9.With the temperature increase,the shear strength of the joint increases first and then decreases with the maximum shear strength of 6.5 MPa obtained at 610 ℃ within 20 min,which fractures at the glass substrate showing brittle fracture.
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