Reinforced calcium aluminosilicate glass-ceramics
The present invention is directed to the production of SiC whisker- and/or fiber-reinforced, internally-nucleated glass-ceramic matrix composite articles consisting essentially of 0.5-60% by weight SiC whiskers and/or 15-70% by volume ceramic fibers substantially uniformly distributed in a glass-ceramic matrix consisting essentially, in weight percent on the oxide basis, of 16-20%, CaO, 38.5-46% Al2O3, 35-42% SiO2, and up to 10% total of at least one nucleating agent in the indicated proportion selected from the group consisting of 0.1-3% Cr2O3, 0.25-3% HfO2, 2-5% MoO3, 0.25-3% Nb2O5, 0.25-3% Ta2O5, 0.25-3% WO3, and 1-10% ZrO2, wherein Al2O3 is present in an amount which is at least 5 mole percent and up to 50 mole percent in excess of that present in stoichiometric triclinic anorthite, and wherein the predominant crystal phases in the glass-ceramic are triclinic anorthite and mullite and/or alpha -Al2O3. Up to 1.5% As2O3 may advantageously be included in the composition.