THRESHOLD CREEP-BEHAVIOR OF ALUMINUM DISPERSION-STRENGTHENED BY FINE ALUMINA PARTICLES

Results of an investigation of creep in aluminium strengthened by 2.6 vol.% fine alumina particles-ODS-2.6Al alloy-are presented with an emp hasis on threshold creep behaviour. At temperatures ranging from 623 t o 723 K the measured minimum creep strain rates covered six orders of magnitude. The true threshold stress sigma(TH) decreases with increasi ng temperature approximately linearly and the same holds for sigma(TH) /G ratio, where G is the shear modulus of the matrix metal-aluminium. The threshold stress is suggested to originate from attractive disloca tion/particle interaction although the detachment stress sigma(d) scal es the temperature dependence of the shear modulus. The minimum creep strain rate (epsilon)over dot(m) is controlled by matrix lattice diffu sion and the true stress exponent n of the minimum creep strain rate i s close to 5. The results for ODS-2.6Al are compared with similar ones for ODS-Al-30SiC(p) composite. From the comparison it follows that th e load transfer effect is absent in this latter composite with heavily dispersion strengthened matrix and that the threshold stress effect p lays the dominant role, similar to that in ODS-2.6Al alloy. (C) 1998 E lsevier Science S.A. All rights reserved.