Abstract: With ZL114A alloy as matrix, ZL114A aluminum matrix composites reinforced by in-situ TiB₂ particles with different mass fractions (3%, 6%, 9%) were prepared by mixed salt reaction method. The microstructure and tensile properties of composites were studied, and the growth mechanism of TiB₂ in the matrix was analyzed. The results show that the main phases of the composites were Al, Si and TiB₂ phases, indicating that the in-situ TiB₂ particle reinforced ZL114A aluminum matrix composites were successfully prepared. With the increase of TiB₂ content, the grains of the matrix were refined and spheroidized, the eutectic silicon was obviously refined and its morphology changed from coarse long strip to short rod. The in-situ TiB₂ particles increased the strength and plasticity of the composite, and the fracture mode changed from brittle fracture of ZL114A alloy to mixed ductile-brittle fracture. With the increase of TiB₂ content, the tensile strength and percentage elongation after fracture first increased and then decreased, and reached the maximum when the mass fraction of TiB₂ was 6%, which were 237.4 MPa and 6.7%, respectively. During the preparation process of the composites, a nearly spherical TiB₂ core was first precipitated from the matrix. With the growth of the spherical core, a small plane was formed on the surface of the spherical core, and finally the typical TiB₂ morphology of the hexagonal platform combination was formed.