On the influence of the crystallization conditions on the microstructure of the directionally solidified eutectic of the LiF-LiYF4 system

This paper particularly deals with the transitions in degree and type of ordering of a given microstructure. As a model system the eutectic of the LiF – LiYF4 system was used for studies of transitions from ‘anomal’ microtextures with non-cooperative production of seeds of both phases to the fibrous microtexture. It was shown that even if the matrix phase LiYF4 contains a relative high volume ratio (36%) of LiF it is possible to create highly ordered fibrous microtextures with pronounced hexagonal ordering of particular LiF fibres. It was also shown that methods of image processing could be used for sensitive evaluation of small changes in degree of ordering of the microstructure. These procedures make possible a deeper understanding of the influence of the solidification conditions on the microstructure of the directionally solidified eutectic and creates possibilities for optimalisation of the technological process.