Effects of mischmetal (RE) and/or Ti modifier on the microstructure includingα-Al dendrites, eutectic Si phases and other secondary phases of Al-Si brazing and/or welding alloys were investigated by differential scanning calorimetry (DSC), optical mi-croscopy (OM), scanning electron microscopy (SEM). The DSC results showed that an addition of RE decreased the eutectic tem-perature and caused supercooling, promoting the nucleation of eutectic Si crystals. In addition, the maximum temperature of the first endothermic peak varied with the different RE contents, which had a good correlation with the microstructural modification of the eutectic Si phase. Theα-Al dendrites were well refined by increasing the cooling rate or adding 0.08 wt.% of Ti. When 0.05 wt.% RE was added to the Al-5Si-0.08Ti alloy, the morphology of eutectic Si phase was transformed from coarse platelet to fine fibers and the mechanical properties of the resulting welding rod were well improved. Whereas, when excess RE was added, a large number ofβ-Fe phases appeared and the aspect ratios ofβ-Fe phases increased. The morphologies and chemical components of two kinds of RE-containing intermetallic compounds (IMCs) were also discussed.