CREEP-BEHAVIOR OF ODS ALUMINUM REINFORCED BY SILICON-CARBIDE PARTICULATES - ODS AL-30SIC(P) COMPOSITE

Results of an investigation of creep behaviour in ODS aluminium reinfo rced by silicon carbide particulates-an ODS Al-30SiC(p) composite-are reported. The minimum tensile creep strain rates were measured at temp eratures 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. Th e creep in the composite is associated with a relatively high true thr eshold stress which decreases with increasing temperature more strongl y than the shear modulus. The true threshold stress is suggested to or iginate predominantly from an attractive dislocation-fine alumina part icle interaction; the presence of SiC particulates does not seem to co ntribute to it significantly. The minimum creep strain rate is matrix lattice diffusion controlled and the true stress exponent of this stra in 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 mi nimum creep strain rate in the ODS Al-30SiC(p) composite is up to 8 or ders of magnitude lower than that in the Al-30SiC(p) composite. This e ffect of strengthening of aluminium matrix by fine alumina particles i s 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-3 0SiC(p) composite. (C) 1998 Elsevier Science S.A. All rights reserved.