Abstract: TiB₂/6061 aluminum matrix composites were prepared by in-situ formation method.The effects of TiB₂ content and heat treatment process on the microstructure and mechanical properties of extruded TiB₂/6061 aluminum matrix composites were studied.The results show that TiB₂ particles have a significant effect on the grain refinement of the composites.As the cooling processed changes from air cooling to water cooling, the strength of the composites is significantly improved.As TiB₂ particle content is 3wt%, the yield strength is increased by 24.9% and the tensile strength is increased by 30%.With the increase of TiB₂ particles content, the strength and elastic modulus of the composites increase significantly.As the content of TiB₂ particles is 3wt%, the tensile strength and elastic modulus of the composite reach the maximum, which are 352 MPa and 78GPa, respectively, which are 8.9% and 16.4% higher than that of 6061 aluminum alloy.The particle agglomeration in the composite is easy to crack and form crack source.As the increase of TiB₂ particles content, the elongation of the composites decreases gradually.