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1993
Conference Proceeding
Titel
Al2O3 and ZrO2 composites with high TIC contents fabricated by tailoring oxide powders
Abstract
Tailored powders give sintering activities of composites with 35 vol-% TiC that equal those of reactive sintering (transient liquid phase by TiH2 addition) and of MgO/Ysub2Osub3 doping, but powder tailoring results in a higher strength. Surprisingly, a tailored Alsub2Osub3 powder processed together with commercial TiC (dsub50 is equal to 1.2 Mym, dsub90 is equal to 10 Mym) gives a higher strength than the use of an extremely fine grained carbide with dsub50 is equal to 0.2 Mym and dsub90 is equal to 0.75 Mym: a bending strength of 800 MPa is achieved without doping additions and without hot-pressing. The reason is a strong impact of oxide dispersion on the milling response of the TiC: the smaller the oxide grain sizes the smaller is the resulting carbide grain size after homogenization milling. With nanoscale ZrOsub2 (3mol-% Ysub2Osub3) and commercial TiC, the carbide grain size in the sintered microstructure is less than 0.5 Mym giving a bending strength of 1100 MPa at a hardness of 1 6.5 GPa. High resolution TEM shows that all grain boundaries are free of amorphous phases.
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