Static and cyclic creep behaviour of SiC whisker reinforced aluminium composite

Abstract

Static and cyclic creep tests were carried out in tension at 573–673 K on a 20 vol.-%SiC whisker reinforced aluminium (Al/SiCw ) composite. The Al/SiCw composite exhibited an apparent stress exponent of 18·1–19·0 at 573–673 K and an apparent activation energy of 325 kJ mol-1 for static creep, whereas an apparent stress exponent of 19·6 at 623 K and an apparent activation energy of 376 kJ mol-1 were observed for cyclic creep. A cyclic creep retardation (CCR) behaviour was observed for the Al/SiCw composite. The steady state creep rate for cyclic creep was three orders of magnitude lower than that for static creep. Furthermore, the steady state creep rates of the composite tended to decrease continuously with increasing percentage unloading amount. The static creep data of the Al/SiCw composite were rationalised by the substructure invariant model with a true stress exponent of 8 together with a threshold stress. The CCR behaviour can be explained by the storage of anelastic strain delaying non-recoverable creep during the onload cycles.