HIGH-TEMPERATURE CREEP-BEHAVIOR OF NANOMETRIC SI3N4 PARTICULATE-REINFORCED ALUMINUM COMPOSITE

Tensile creep tests were carried out on the commercially pure aluminum reinforced with amorphous nanometric Si3N4 particulates at 573, 623 a nd 673 K. The creep resistance of the nanometric Si3N4 particulates co mposite was about two orders of magnitude higher than that of the micr ometric 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 nanometr ic particulate composites exhibited an apparent stress exponent rangin g 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 incre asing temperatures. The creep data were rationalized using a substruct ure-invariant model with a stress exponent of 8 together with a thresh old stress. The transmission electron microscope observations proved t he invariance of the microstructure of the composite during the creep deformation. (C) 1997 Elsevier Science S.A.