<p>In this work, Mg₂Si particles reinforced A6061 composites were prepared by hot extrusion and T6 heat treatment. The microstructure, age-hardening behavior, and mechanical properties of the T6-treated Mg₂Si/A6061 composites were investigated. Microstructural observations showed that micro-sized Mg₂Si particles and nano-sized β″ precipitates were uniformly distributed in the matrix. However, significant amounts of MgAl₂O₄ were formed near the Mg₂Si/A6061 interfaces, resulting from the reaction between Mg (sourced from the A6061 matrix and Mg₂Si particles) and oxidation film on the surfaces of the A6061 powder. The precipitation and growth of β″ precipitates in the composites proceeded smoothly with increasing the aging time, revealing that the loss of Mg in the matrix might be compensated by the Mg diffused from the incorporated Mg₂Si particles. As a result, the Mg₂Si/A6061 composites exhibited age-hardening behavior similar to that of the unreinforced A6061 alloy. Although the peak-aged composites presented limited ductility, their hardness, strength, and wear resistance were superior to those of the peak-aged A6061 alloy. This enhancement is attributed to the synergetic strengthening effects of Mg₂Si particles, MgAl₂O₄ phase, and β″ precipitates.</p>