| Undoubtedly, magnesium alloys are one of the lightest materials in various engineering fields. Magnesium alloys have become very valuable green materials, based on its excellent thermal conductivity, electromagnetic shielding, damping resistance and ease of processing characteristics.In this paper, the research on magnesium alloy (AZ31B, ME20M and AZ91D) by contact reactive brazing (CRB) in furnace, Copper foil, BA188SiMg and Zn sheet were selected as the intermediate layers. Microstructure, element behavior and mechanical properties with different process parameters were analyzed by apparatus of optical microscope, scanning electron microscopy (SEM) accompanied by EDS and Micro Hardness Tester. The good brazing joint status was obtained by the optimization of the technological parameter.The results show that good welding joint surface can be obtained under proper brazing parameters. CRB with Zn, Cu and BA188SiMg intermediate layer have dissolution tendency to three base metals. Main factors of dissolution were brazing temperature, holding time and thickness of intermediate layers.BA188SiMg as the intermediate layer of brazing ME20M and AZ31B, the more obvious disordered crystal structure was formed in the joint cross-section. With the heating temperature, the liquid layer expanded to the base metals and got an increasing width. Based on zinc as an intermediary, due to the strong reaction between Zn and Mg, and the high volatility of Zn, the joint will produce the defects such as holes, reducing the continuity of the joint. Cu as the intermediate layer of the brazing AZ31B, with the increase of peak temperature, the mutual diffusion between elements was further strengthened. The liquid layer composed by melting Cu foil widened gradually by dissolving the near solid base. As the peak temperature continues to rise, the middle layer is no longer widening. The interface between base metal and the middle layer formed obvious diffusion reaction zone. |
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