Creep behaviour of ODS aluminium reinforced by silicon carbide particulates:: ODS Al-30SiCp composite

Results of an investigation of creep behaviour in ODS aluminium reinforced by silicon carbide particulates-an ODS Al-30SiC(p) composite-are reported. The minimum tensile creep strain rates were measured at temperatures of 623, 673 and 723 K; applied stresses ranged from 2.77 x 10(-3) to 7.74 x 10(-3) G, where G is the shear modulus of aluminium. The creep in the composite is associated with a relatively high true threshold stress which decreases with increasing temperature more strongly than the shear modulus. The true threshold stress is suggested to originate predominantly from an attractive dislocation-fine alumina particle interaction; the presence of SiC particulates does not seem to contribute to it significantly. The minimum creep strain rate is matrix lattice diffusion controlled and the true stress exponent of this strain rate is close to 5. In this respect, the creep behaviour of the ODS AI-30SiC(p) composite is similar to that of an Al-30SiC(p) composite. Depending on the conditions of applied stress and temperature, the minimum creep strain rate in the ODS Al-30SiC(p) composite is up to 8 orders of magnitude lower than that in the Al-30SiC(p) composite. This effect of strengthening of aluminium matrix by fine alumina particles is largely, but not entirely, due to the higher threshold stress in the ODS Al-30SiC(p) composite. Some other possible contributions to this effect are discussed, but the load transfer is not considered to play any significant role in the heavily alumina particle strengthened AI-30SiC(p) composite. (C) 1998 Elsevier Science S.A. All rights reserved.