FABRICATION OF DENSE, LIGHTWEIGHT, OXIDE-RICH OXIDE/ALUMINIDE COMPOSITES AT 1000 deg C BY THE DISPLACIVE COMPENSATION OF POROSITY (DCP) PROCESS

摘要

Dense, lightweight, oxide/aluminide composites of high oxide content have been fabricated using a novel, reactive infiltration approach at modest temperatures: the Displacive Compensation of Porosity (DCP) method. This process involves the pressureless infiltration of a shaped, porous ceramic perform by a metallic liquid that can undergo a displacement reaction with the perform. Because a larger volume of ceramic is produced than is consumed in the DCP process (unlike for other reactive infiltration processes), the pore volume within the perform can be filled upon complete reaction (i.e., reaction-induced densification) so as to yield a dense, ceramic-rich composite. This paper demonstrates the feasibility of producing MgO-rich, MgO/FeAl intermetallic composites using the DCP method. Mg(1) was allowed to infiltrate into, and then react with, porous MgAl_2O_4MgO/Fe-bearing performs at <= 1000 deg C and at ambient pressure. Dense, lightweight composites comprised of fine, intimate, MgO-rich mixtures with FeAl were produced within 24 minutes at a peak temperature of 1000 deg C.