| Magnesium and its alloys have been widely used in various fields for their excellent properties such as high specific strength, low density, good and economical process ability with cast technology, and high recycling potential. For the low-density, low melting point, high thermal conductivity, high electrical conductivity and thermal expansion coefficient, chemical activity and easy to oxidation, Magnesium alloy brazed by the traditional welding prone to hot welding cracks, pores, alloying elements and the weld zone softening burning, which limited the application of magnesium in the field of aircraft, automobile and ship. The connection between Magnesium alloy structural parts has become a constraint obstacle to the application of magnesium.As opposed to fusion welding and pressure welding, brazing with the low heating temperature, small weldment distortion, beautiful shape, and high production efficiency, is especially suitable for connecting precision, miniature and complex, welding parts. At present, magnesium alloy brazing technology is not yet very mature. Therefore, the development of magnesium alloy brazing alloy is of great significance to promote the development of magnesium alloy welding technology. So in this paper, new kinds of solder alloys were developed for brazing AZ31B and Mg/Al. Correlative technological parameters were investigated to refine the structure of the bond region.The investigation prepared the Mg-Al-Zn solder alloys for AZ31B and extended them to the brazing AZ61, AZ91 and Mg/Al. Basic on the characteristics of brazing Mg/Al, the research also prepared Zn-Mn and Zn-Sn alloys. The alloys were prepared through crucible melting and flux protecting. Their melting characteristics, spread abilityies, metallographic structures and typical fracture morphologies of joints were analyzed by spreading and wetting capacity test, scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray spectroscopy (EDXS) analysis system. The results are as follows: 1) The filler metals had good melting and wetting abilities. The solid-liquid temperature range was less than 15℃, which was conducive to the brazing, the largest wetting area was 1536 mm2 and the wetting angle was 13.3°. The compositions were also satisfied to the requirement of brazing.2) Results of microstructure observation showed that Zn-enriched phases disappeared andα-Mg existed in the joints in the form of coarse dendrites by increasing the concentration of Mg in the solder alloys. Water cooling with a high cooling rate restricted the grains ofα-Mg as the equiaxed dendrites, which was about 1/5 of the coarse dendrite but the number of them was more than 40-50 times. Both morphology with typical fracture and the analysis on X-ray diffraction fracture indicated that equiaxed dendrites significantly improved the mechanical property of the joints. Necking phenomenon occurred in the bonding region improved the joint shear strength to 80.42MPa.3) Joints of Mg-Al-Zn solder alloy brazing AZ61 and AZ91 showed the same microstructure to AZ31B joint. The joint shear strength was at the level of to 70MPa. The result showed that Mg-Al-Zn solder alloy was also fit to brazing AZ61 and AZ91.4) Mg-Al-Zn solder alloy was also used to brazing Mg/Al. Basic on the characteristics of brazing Mg/Al, Zn-Mn and Zn-Sn brazing alloys were prepared. Research indicated that the diffusion of base metals participated in the joint formation, which indicated that high brazing temperature and elements content of Mg or Al in solder alloy would accelerate the brittle intermetallics between Mg/Al. Soldering temperature of Sn-Zn was far lower than the reaction temperature, thereby the diffusion between Mg/Al was restricted and the formation of brittle intermetallics was avoided. Soldering with Sn-Zn alloy was succeeded in joining Mg/Al.
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