The primary phase part in microstructure formation of in-situ eutectic composite of LaB₆-ZrB₂

• Main Authors: Ereshchenko, A.A., Paderno, Yu.B., Filippov, V.B., Paderno, V.N.
• Format: Article
• Language: English
• Published: НТК «Інститут монокристалів» НАН України 2005
• Series: Functional Materials
• Online Access: http://dspace.nbuv.gov.ua/handle/123456789/139312

The crystal orientation relationships (COR) of LaB₆-ZrB₂ eutectic phase produced by directional solidification (DS) correspond to non-optimum coherency conditions of phase boundaries. Another peculiar feature of this eutectic is the dominant role of primary low temperature phase (LaB₆) in the cooperative eutectic growth. As a rule, it is just the high-temperature phase that plays a leading role in the crystallization and promotes heterogeneous nucleation of the second phase. In contrast, in LaB₆-ZrB₂ eutectic system, the high-temperature ZrB₂ whiskers start to grow on (100) faces of low-temperature LaB₆ phase. A possibility of discrete changes in growth direction of the composite regular structure up to 90⁰ has been revealed. It is suggested that all above mentioned features are defined mainly by the nucleation processes during the eutectic co-crystallization process, rather than by the ordinary fundamental criteria of interface surface energy minimization that occurs due to the semi-coherent habit facets formation.