Effects of minor Zr addition on the microstructure and mechanical properties of laser welded joint of Al/SiCp metal-matrix composite

Laser butt welding (LW) joints of aluminum-matrix composite with 10 vol% silicon carbide particle (SiCp) was compared between with and without the addition of zirconium (Zr). By adding zirconium (Zr) to the molten pool, ultimate tensile strength (UTS) of the joints were increased from about 65% of the UTS of the parent material (BM) to the equal UTS of BM. It was found that, by adding minor Zr into molten pool, porosity defects in welded seam zone (WM) disappeared; the residual SiC particles in WM were tightly bonded with the surrounding matrixes; generation of large size brittle phase Al4C3 was inhibited in the WM; fine ZrC precipitates with the size of 5-10 mu m was generated and uniformly distributed in the WM zone. These results highlight the possibilities for strengthening fusion welded joint of Al/SiCp metal-matrix composite by taking Zr as alloying element.