Cast aluminum matrix composites are promising materials for the production of responsible and particularly critical parts used in the high-technology fields of industry such as aerospace, automotive, electronics, etc. In this work, hybrid aluminum matrix composite reinforced with in-situ formed Mg2Si and Al3Ti particles were synthesized successfully in gravity casting conditions, and the influence of thermal conditions of solidification on the structural parameters of endogenous reinforcing phases was investigated. The results show that an increase in the cooling rate during solidification due to the application of a copper mold instead steel mold leads to reduction in the average size of the Mg2Si primary crystals, improvement of the distribution uniformity and significant increasing of their total quantity; at the same time, the average size of Al3Ti particles decreases substantially but their quantity is approximately the same for both types of molds.