Study on the microstructure of LaB₆-ZrB₂ in-situ composite

LaB₆-ZrB₂ eutectic in-situ composite was prepared by use of an electron beam zone heating technique, and oriented ZrB₂ fibers in a LaB₆ matrix was obtained. The range of diameter of the ZrB₂ fibers was 0. 2-1. 2 μm with fiber lengths up to 100 μm. As the solidification rate increases, the interfiber spacing and fiber diameter decrease. Primary plate-like LaB₆ dendrites formed upon the solidification of an ingot with a 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 growth the orientation relation of the phases was: Growth direction: [001]LaB₆//[00. 1]ZrB₂ Interfacial plane: (1̄10)LaB₆//(11. 0)ZrB₂.