Internal friction in microcrystalline magnesium reinforced by alumina particles

Using internal friction measurement, changes in the microstructure of micro crystalline magnesium and magnesium with 3 vol.% of Al2O3 microparticles an d nanoparticles, due to thermal treatment, have been investigated. Material s have been thermally treated at increasing temperature and then the amplit ude dependence of the logarithmic decrement was measured at room temperatur e. The thermal treatment influences the amplitude-dependent component of th e decrement in composite with nanoparticles while in composite with micropa rticles no influence has been estimated. Thermal stresses induced in the co mposites due to a difference between thermal expansion caefficient of matri x and ceramic particles may create new dislocations during the cooling from elevated temperatures. Density of new dislocations depends on the particle size. The thermal stresses can achieve yield stress in the matrix and micr o-glide of newly created dislocations as well as their annihilation may occ ur. (C) 2000 Elsevier Science S.A. All rights reserved.