Study on Novel Powder Metallurgy Al-Si Brazing Filler Metal with Flux

Abstract

Green brazing is one of the key basic technologies in the manufacturing industry, and the wide application of composite brazing filler metals is a significant method for realizing green and automatic brazing. In the present study, an investigation was conducted into a novel powder metallurgy Al-Si brazing filler metal with flux and the resulting brazed joints of 3003/6061 aluminum alloy. By means of scanning electron microscopy and energy-dispersive analysis, the effect of moisture-resistance performance on the microstructure and the properties of Al-Si brazing filler metal with flux and brazing joint were analyzed. The results reveal that the new type of powder metallurgy Al-12Si brazing filler metal had better moisture-resistance performance than the seamed flux cored brazing filler metal. In an environment with a humidity of 90% and a temperature of 40 °C for 7 days, the moisture absorption rate of the powder metallurgy Al-12Si brazing filler metal with flux was only 0.17%. The wet spreading area of the new powder metallurgy Al-12Si brazing filler metal treated for 3 days in a humid environment was 320 mm2, which was 7% less than that in the dry state. At the same time, the spreading area of the seamed flux cored brazing filler metal under the same conditions was only 80.9% of that in the dry state. The fracture strengths of the 3003 and 6061 aluminum alloy joints brazed by the wetted powder metallurgy Al-12Si brazing filler metal with flux were satisfactory, and scanning electron microscopy examination of the braze-zone revealed that relatively sound joints were obtained. However, obvious pores were observed in the braze-zone of the wetted seamed flux cored brazing filler. The maximum diameter of the pores was increased from 28 μm to 68 μm in the brazing area.