High temperature creep behavior of nanometric Si3N4 particulate reinforced aluminium composite

Tensile creep tests were carried out on the commercially pure aluminum reinforced with amorphous nanometric Si3N4 particulates at 573, 623 and 673 K. The creep resistance of the nanometric Si3N4 particulates composite was about two orders of magnitude higher than that of the micrometric SiC particulate composite. The steady state creep rate of the nanometric Si3N4 particulates composites was somewhat decreased at 573 K with increasing Si3N4 vol. percent from 1 to 2. However, the creep rates at 623 and 673 K were independent of Si3N4 content. The nanometric particulate composites exhibited an apparent stress exponent ranging from 13.41 to 16.47 and an apparent activation energy of 221–259 kJ mol−1. The apparent stress exponents appeared to decrease with increasing temperatures. The creep data were rationalized using a substructure-invariant model with a stress exponent of 8 together with a threshold stress. The transmission electron microscope observations proved the invariance of the microstructure of the composite during the creep deformation.