STRUCTURE CHARACTERISTICS AND CRYSTALLOGRAPHY OF LAB6-ZRB2 IN-SITU COMPOSITE

LaB6-ZrB2 eutectic in-situ composite was fabricated by use of an elect ion beam zone heating technique, and orientated ZrB2 fibers in a LaB6 matrix were obtained. The range of diameter of the ZrB2 fibers was sim ilar to 0.2-1.2 mu m, with fiber lengths up to 100 mu m. As the solidi fication rate increases, the interfiber spacing and fiber diameter dec rease. Primary plate-like LaB6 dendrites formed upon the solidificatio n of an ingot with hypoeutectic composition. LaB6 was the first phase to nucleate when eutectic growth occurred, and ZrB2 showed non-faceted growth in the hypereutectic. For the ingot solidified with planar gro wth the orientation relation of the phases was Growth direction: [001] LaB6//[00.1]ZrB2, Interfacial plane: (<(1)over bar 10>)LaB6//(11.0)ZrB 2.