Brittle intermetallic compounds are prone to form in dissimilar joints, which significantly affected the reliability of the joints. To avoid or control the production of brittle intermetallic compounds, an inclined butt joint of 5A06 Al and AZ31B Mg alloys with 20 mm thickness using friction stir welding was designed. Microstructures and chemical composition of the joint were investigated by optical microscopy, scanning electron microscopy, micro X-ray diffraction, transmission electron microscopy. The intermetallic compounds in the weld nugget zone presented different precipitation behavior along the thickness direction. In the upper of the weld nugget zone, intermetallic compounds Al₃Mg₂, Al₁₂Mg₁₇, and non-equilibrium phase AlMg precipitated during solidification due to excessively high temperature of the upper of the weld nugget zone. The Al₃Mg₂ phase merely precipitated and grown along the grain boundaries in the middle and lower of the weld nugget zone. The maximum Vickers hardness value was approximately 289 HV, which was obtained at the upper of the Mg side interface, existing a thick eutectic zone consisted of Mg and Al₁₂Mg₁₇. The nanohardness of the Al₁₂Mg₁₇ layer and the Al₃Mg₂ layer were 5.39 GPa and 4.18 GPa, respectively. The precipitation of the Al₁₂Mg₁₇ and the Al₃Mg₂ phases plays a precipitation strengthening effect.

脆性金属间化合物易于在异种接头中形成，这严重影响了接头的可靠性。为避免或控制脆性金属间化合物的产生，设计了采用搅拌摩擦焊的20毫米厚度的5A06 Al和AZ31B Mg合金的斜对接。通过光学显微镜，扫描电子显微镜，微X射线衍射，透射电子显微镜研究了接头的微观结构和化学成分。熔核区域中的金属间化合物沿厚度方向表现出不同的析出行为。在焊接熔核区的上部，金属间化合物Al ₃ Mg ₂，Al ₁₂ Mg ₁₇由于熔核区域上部的温度过高，在凝固过程中会析出非平衡相AlMg。Al ₃ Mg ₂相仅在熔核区域的中下部沿着晶界析出并生长。最大的维氏硬度值约为289 HV，这是在Mg侧界面的上部获得的，存在一个由Mg和Al ₁₂ Mg ₁₇组成的厚共晶区。Al ₁₂ Mg ₁₇层和Al ₃ Mg ₂层的纳米硬度分别为5.39 GPa和4.18 GPa。Al ₁₂ Mg ₁₇的沉淀Al ₃ Mg ₂相起着析出强化作用。