The dilatation characteristics of the continuosly cast AZ31 alloy and composite with AZ31 matrix reinforced by SiC nanoparticles were investigated in the temperature range of 20-410 °C. The axis of specimens was either parallel or perpendicular to the casting texture. The linear thermal expansion of the alloy as well as the composite was measured in an argon protective atmosphere using a Netzsch 410 dilatometer. The relative elongation and coefficient of thermal expansion are the main experimental results obtained using dilatometry. The temperature dependence of the elastic modulus can be calculated using analysis of the dilatometry results.