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 particles and reinforced by silicon carbide particulates is investigated. For comparison, the results for two dispersion strengthened (DS) AlC alloys denoted DS AlC1 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 AlC alloys as well as in SiC/AlC composite matrices). The volume fraction of SiC particulates in composites, denoted SiC/AlC1, SiC/AlC2 and SiC/AlC3, was fixed to 10 vol.%. The creep in both DS AlC alloys as well as in SiC/AlC composites is associated with relatively high true threshold stress σTH. 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 rate was found to be controlled by lattice diffusion in the matrix metal–aluminium. The creep strength of the SiC/AlC composites increasing with the volume fraction of Al4C3 particles is entirely due to the effect of this fraction on the threshold stress. This is not the case of DS AlC alloys. The difference 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.