Creep behaviour of aluminium strengthened by fine aluminium carbide particles and reinforced by silicon carbide particulates - DS Al-SiC/Al4C3 composites

Creep behaviour of aluminium strengthened by fine aluminium carbide particl es and reinforced by silicon carbide particulates is investigated. For comp arison, the results for two dispersion strengthened (DS) AlC alloys denoted DS AlCl and DS AlC2 are presented. (C1 and C2 mean the contents of carbon in wt% which define the volume fractions of Al4C3 particles in DS AIC alloy s as well as in SiC/AlC composite matrices). The volume fraction of SiC par ticulates in composites, denoted SiC/AlCl, SiC/AlC2 and SiC/AlC3, was used to 10 vol.%. The creep in both DS AIC alloys as well as in SiC/AlC composit es is associated with relatively high true threshold stress sigma(TH). The linear regression analysis showed that the true stress exponent of minimum creep strain rate of 8 should be preferred to that of 5. The creep strain r ate was found to be controlled by lattice diffusion in the matrix metal-alu minium. The creep strength of the SiC/AlC composites increasing with the vo lume fraction of Al4C3 particles is entirely due to the effect of this frac tion on the threshold stress. This is not the case of DS AlC alloys. The di fference of the creep strength in SiC/AlC composites and the respective DS AlC alloys could be accounted for by the load transfer effect. The athermal detachment of dislocations from fine Al4C3 (and Al2O3) particles dispersed in the composite matrix is considered as the creep strain rate controlling process. (C) 1999 Published by Elsevier Science S.A. All rights reserved.