In situ observation and interferometric characterization of solid-liquid interface morphology in directionally growing transparent model systems

The performance of a new directional solidification device dedicated to the characterization of solid-liquid interface morphology by means of optical methods is presented in this paper. In contradiction to usual solidificatio n studies on transparent materials carried out on thin films, which elimina tes the complex coupling between solidification and convection, this device enables in situ and real time studies on bulk transparent materials. The a lloy is contained in a cylindrical crucible and observation is performed in two perpendicular directions: the growth one and the transverse one. In ad dition to direct observation by light transmission in those directions, an interferometer is also set up in the growth direction to provide informatio n on the shape and the motion of the interface through an analysis of the i nterferometer fringes. The combined determination of solidification front c haracteristics by these three observation modes has already given critical information on interface dynamics: front recoil measurements during initial transient. formation of microstructure patterns, and influence of convecti on on the triggering of instabilities.