A SiC particulate reinforced 1040 commercially pure aluminum was thermally cycled in air between 20 and 300 degrees C up to 500 cycles. And the damping capacities of the specimens after 50 and 500 cycles were measured against temperature and strain amplitude. Thermal cycling causes the increase in damping, and dislocation damping is the main mechanism. A damping peak was observed in the range of 150-200 degrees C, which is related to dislocation motion. Thermal cycling leads to the increase in the peak temperature. The activation energy of the internal friction peak was calculated by Arrhenius equation, yielding 1.02 and 1.09 eV for 50 and 500 cycles, respectively. Increase in dislocation during thermal cycling is responsible for the increase in peak temperature and activation energy.