Casting of metal matrix composites is an attractive process since it offers a wide selection of materials and processing conditions. Among the casting methods, melt-stirring technology is much attractive route in industrial application because it is more simple and inexpensive compared to squeeze casting or powder metallurgy. In the present work, effects of particle size, volume fraction of particles and mg addition on mechanical properties and thermal expansion coefficients of $alpha$ -$Al_2O_{3(p)}$/LXA composites were studied. It is shown that $alpha$ -$Al_2O_3$ particles formed at the interface of $alpha$ -$Al_2O_3$ particles and matrix made an important role on mechanical properties. Ultimate tensile strength of most composite materials was not increased. But in the case of 5vol% addition of 16$mu extrm{m}$ $alpha$ -$Al_2O_3$ Particle, Ultimate tensile strength of composite materials with 3wt.% Mg was increased. Volume fraction of reinforcements and mg content were thermal expansion coefficients of composite materials were decreased.