Abstract: The weldability of in-situ TiB₂ particulate reinforced ZL101 Al metal matrix composites by high power laser welding was studied.The studied results show that TiB₂ particles increase the viscosity and decrease the fluidity of molten pool,so the sensitivity of porosity is improved and at the same time weld appearance becomes bad.The hydrogen porosity as mainly pores distributes at the bottom of molten pool and around the fusion line.The grains of weld seam are much finer than that of base metal because of higher cooling rate.There is no segregation and TiB₂ particles distribute homogeneously in the weld seam because nanometer TiB₂ particles are not removed but trapped by the solid-liquid interface during the process of solidification.According to the results of X-ray diffraction and TEM,there are no interface reaction products such as brittle Al₃Ti or AlB2 between the matrix and TiB₂ particles.The interface between TiB₂ and Al matrix is smooth and the reinforcing effect of TiB₂ is still unchanged.