Development of a Mg-Al filler metal for brazing magnesium alloy AZ31B

A Mg-Al filler metal was used to braze magnesium alloy AZ31B through furnace brazing under the protection of a flux. There are two microstructures in the filler metal: solid solution ɑ-Mg and eutectic structure ɑ-Mg+γ-Mg₁₇Al₁₂. The microstructure and mechanical properties of the brazed joint were investigated. According to the experimental results, partial base metal was dissolved into the brazing seam during the brazing process, where ɑ-Mg solid solution and γ-Mg₁₇(Al, Zn)₁₂ compound were formed. The average shear strength of the brazed joints is 75 MPa. The fracture morphology of the brazed joint exhibits a intergranular brittle feature. Discontinuous γ-Mg₁₇(Al, Zn)₁₂ phase distributed around the ɑ-Mg grains is a main crack source.