Steady state creep deformation behaviour of SiC particle reinforced 2618 aluminium alloy based composites

Tensile creep behaviour of 2618 aluminium alloy based composites reinforced with 15 vol.-%SiC particles (SiCp) of 3.5 and 10 mu m at 423-673 K was inv estigated. The results showed that the composites reinforced with both smal l and large SiC particles exhibited apparent stress exponents of 7.1-10.2 a nd 8.3-25.2, and apparent activation energies of 314 kJ mol(-1) and 344 kJ mol(-1), respectively. Moreover; a critical stress was observed in the comp osite specimens, below which the creep resistance of the 2618 + SiCp (3.5 m u m) composite was higher than that of the 2618 + SiCp (10 mu m) composite. Above this value, the for mer was less creep resistant than the latter. Se veral established models were used to rationalise the creep data of these t wo composites at higher temperatures. The analyses revealed that the creep data for the 2618 + SiCp (3.5 mu m) composite cannot be rationalised with a stress exponent of 8 or 5 while those for the 2618 + SiCp (10 mu m) compos ite can be reasonably rationalised by a climb controlled dislocation creep model with a stress exponent of 5. On the other hand the 2618 + SiCp (10 mu m) composite crept at lower temperatures (below 0.51T(m), where T-m is the melting point of aluminium in Kelvin) exhibited stress exponents of 13.0 a nd 6.5 at 423 and 473 K, and activation energies of 85 and 182 kJ mol(-1) i n the vicinity of 423 and 473 K, respectively. The creep behaviour of the,2 618 + SiC, (10 mu m) composite at 423 K can be interpreted in terms of the dislocation pipe diffusion.