Thermal stress relaxation in magnesium matrix composites studied by mechanical spectroscopy

Thermal stress relaxtion at the interfaces in magnesium matrix composite has been studied by mechanical spectroscopy. Two specimens were processed by a gas pressure infiltration method. In one sample, the metallic matrix was unidirectionally oriented with respect to the matrix-reeinforcement interface by a Bridgeman technique, while the other was kept as infiltrated. The results show a strong dependence of the damping on the orientation of the matrix. The results are compared with a model of thermal stress relaxation by dislocation motion controlled by a solid friction mechanism. A fitting parameter proportional to the mobile dislocation density is obtained showing the entire evolution of the mobile dislocation density with respect to the temperature.