Study On Microstructures And Mechanical Properties Of Filler Metal And Brazed Joint Of Magnesium Alloy

Magnesium alloy is wildly used in the fields of aviation, space flight, automobile, computer calculator and electron electronic due its advantage of light, abundant and a series of excellent performance. So magnesium alloy is considered as green engineering materials and important commercial lightweight structural materials. At present, in spite of the wild application of die casting magnesium alloy, wrought magnesium alloy would be processed to more complex structures if reasonable connection method is used. Therefore, magnesium alloy welding became the research hotspot. Compared to fusion welding, the soldering is a method that the parent metal does not melt and the material clearance molten state is filled by filler metals rely on capillary action. The temperature of soldering is lower than the melting welding, so the parent metal thermal deformation is small and soldering is suitable for the connection of precision parts which is high size requirement. However, the low melting point magnesium solder needs to be studied due to high melting point of now commonly used magnesium alloy solder.According to basic design principles of solder, Mg58.5A131.5Snl, Mg55.5A128Sn16and Mg69.5Zn29.5Snl solders were designed for high frequency induction soldering of AZ31B magnesium alloy under argon protection. In order to obtain a good performance solder, the structure and mechanical properties of the designed solders and AZ31B braced joint was investigated by metallographic microscope, Scanning electron microscope, energy spectrum analysis, X-ray diffraction analysis and tensile test, and misch metal was added to optimize the properties of the obtained solder. Afterwards, optimized solder was used to soldering AZ61magnesium alloy and the structure and mechanical properties of the braced joint was analyzed.The results showed that good quality brazed joint AZ31B magnesium alloy were obtained by the three the designed solders. The brazed joint using Mg58.5A131.5Sn10solder owned highest tensile strength, which is51.6N/mm2. The melting temperature range of the solder was443--457℃and the spreading areas was635.31mm2. With the addition of misch metal, the melting temperature range of the solder changed to 427～438℃and the spreading areas became775.42mm2. Moreover, the tensile strength increased to59.67N/mm2, due to the refinement effect of misch metal to the structures.Good quality brazed joint of AZ61magnesium alloy were obtained using Mg58.5A131.5Sn10and Mg58.1A131Sn9.9RE solders and the corresponding tensile strength were45.4N/mm2and49.3N/mm2, respectively. Compared with brazed joint of AZ31B magnesium alloy, the tensile strength of AZ61brazed joint was lower.