Abstract: After the surface of 1100-H14 Al alloy plate was machined into rectangular grooves which were then filled with Ti powder,the layer of Al₃Ti-Al composites was obtained by friction stir processing(FSP).The microstructures,phase compositions and hardness of the layer were analyzed by scanning electron microscopy,EDS and X-ray diffraction.The results show that Ti particles are severely broken under the thermal-mechanical coupling process of FSP,and the broken Ti particles rapidly react in situ with Al matrix and synthesize micron or sub-micron particles of Al₃Ti.Owing to the homogeneous distributions of Al₃Ti and residual Ti particles in the Al matrix,the microhardness of the layer reaches 71.39 HV,which is 2.1 times of the base metal.