The displacive compensation of porosity (DCP) method for fabricating dense, shaped, high-ceramic-bearing bodies at modest temperatures

A novel process is introduced for the fabrication of dense, shaped ceramic/ metal composites of high ceramic content: the Displacive Compensation of Po rosity (DCP) method. In this process, a metallic liquid is allowed to infil trate and undergo a displacement reaction with a porous oxide preform. Unli ke other displacement-reaction-based processes (e.g., the C-4, RMP, and AAA processes), a larger volume of oxide is generated than is consumed, so tha t composites with relatively high ceramic contents can be fabricated. Bar- and disk-shaped MgO/Mg-Al composites were produced by the infiltration and reaction of molten Mg with porous Al2O3 preforms at 1000 degrees C. By vary ing the relative density of the preforms (from 53.3 to 71.0% of theoretical ), the magnesia content of the final composites could be adjusted from 70.4 to 85.6 vol %. Because the increase in oxide volume associated with the co nversion of alumina into magnesia was accommodated by the prior pore volume of the preforms, the composites retained the shapes and dimensions (to wit hin a few percent) of the starting preforms. The MgO/Mg-Al composites were lightweight (2.94-3.30 g/cm(3)), dense (97.7-99.0% of theoretical), and res istant to hydration. Bar-shaped MgO/Mg-Al composites exhibited average flex ural strength and indentation toughness values of 244 MPa and 5.4 MPa . m(1 /2), respectively. (C) 1999 Kluwer Academic Publishers.