Brazing filler metal suitable for braze welding of magnesium-aluminum dissimilar alloys and preparation method for brazing filler metal

The invention discloses a brazing filler metal suitable for braze welding of magnesium-aluminum dissimilar alloys, wherein the brazing filler metal consists of the following components in percentage by weight: 25-35wt% of Mg, 25-35wt% of Al, 20-30wt% of Zn and 20-30wt% of Sn. The invention further discloses a preparation method for the brazing filler metal, wherein the preparation method comprises the following steps: (1) preparing raw materials; and (2) smelting the raw materials. The brazing filler metal is used for braze welding of the magnesium-aluminum dissimilar alloys, so that the direct contact of magnesium alloy and aluminum alloy is avoided, and generation of an intermetallic compound is effectively avoided; and the shearing strength and the tensile strength of an alloy joint obtained by virtue of braze welding of the brazing filler metalare greatly improved, so that the joint properties of the magnesium alloy and thealuminum alloy are improved, and therefore, the welding is firmer. The preparation