Critical factors in the templated grain growth of textured reaction-bondedalumina

The Templated Grain Growth (TGG) of Al2O3 occurs in three stages: densifica tion, radial growth of individual template grains until template impingemen t, and template grain thickening. Significant template growth occurs only a fter densification to similar to 90% density. Template Loading determines t he intertemplate spacing and, subsequently, the degree of growth. The spaci ng distance can be predicted from the initial template concentration and te mplate dimensions, Thermodynamic conditions favorable for template growth o ccur when the size ratio between the template thickness and matrix grains i s greater than or equal to 1.5. The initial template concentration should b e less than a critical template concentration, V-T,V-C, to achieve textured ceramics with a narrow orientation distribution. For this system, which us es 20 +/- 5 mu m x 2 mu m template particles and uniaxial pressing as a for ming technique, V-T,V-C is between 5 and 10 vol%.