FABRICATION AND MICROSTRUCTURAL EVALUATION OF ZRB2 ZRC/ZR COMPOSITES BY LIQUID INFILTRATION/

The microstructure of ZrB2/ZrC/Zr composites was examined using scanni ng electron microscopy, optical microscopy, and X-ray diffraction tech niques. Dense ZrB2/ZrC/Zr composites could be fabricated by the reacti on sintering of molten zirconium with ZrB2 preform. The composites wer e made by infiltration of molten zirconium into ZrB2 preform, which co ntained 0-40 vol % B4C, at 1900 degrees C for 10 min. The average grai n size of ZrB2 in the reaction-sintered composites decreased slightly with an increase in the volume fraction of the B4C. The volume fractio n of the solid increased with further increase of B4C contents. The me chanical properties were measured in accordance with B4C contents. The composites exhibited a four-point bending strength of up to 570 MPa a nd a fracture toughness of up to 11.5 MPam(1/2).