The high-temperature creep behaviour of aluminium-matrix composites reinforced with SiC, Al2O3 and TiB2 particles

Tensile creep tests have been carried out on particulate composites with matrices of aluminium and Al/3.2 wt% Cu alloy at 573 and 623 K. Particulate SiC was incorporated in these alloys which also contained particles of Al2O3 and TiB2 grown in situ during processing. The results showed that the pure aluminium-based composites exhibited art apparent stress exponent of 8.9 and 9.5, respectively, at 573 and 623 K, and an apparent activation energy of 177 kJ mol(-1). The composites based on the Al-Cu alloy exhibited an apparent stress exponent of 11.9 and 13.2 at 573 and 623 K, respectively, and an apparent activation energy of 323 kJ mol(-1). The creep resistance of the Al-Cu alloy composite was about two orders of magnitude higher than that of the pure aluminium composite. The creep data for the two composites were rationalised by using a substructure-invariant model with a stress exponent of 8 together with a threshold stress. The threshold stresses obtained from the extrapolation technique tended to decrease with increasing temperatures for these two composites. (C) 1997 Elsevier Science Limited.