Optical device dedicated to the non-destructive observation and characterization of the solidification of bulk transparent alloys in situ and in realtime

An optical system has been developed to characterize transparent organic al loys during their directional solidification in situ and in real time insid e bulk samples with a high aspect ratio. Standard solidification experiment s are performed within thin glass slides where solidification behaviour is modified compared with bulk solidification due to the space constraint. On the other hand, the interface can be easily observed via a microscope. For bulk samples, a more complex system had to be implemented. We designed a sp ecific glass observation cell and an adapted solidification furnace. Optica l elements were integrated inside the glass observation cell containing the solidifying alloy. The resulting glass observation cell can be easily used as a tool for many optical characterization methods. Here we use the system to generate live i mages of the solid-liquid interlace. These images, recorded on video, provi ded very interesting and fruitful information on the dynamic phenomena appe aring at the interface. The whole interface as well as specific details of the interface could be observed. The images showed a resolution of a few mi crometres, suitable to characterize interface features, as well as a high c ontrast and a constant magnification. As a consequence, further image proce ssing to quantitatively characterize the solid-liquid interface could be ea sily performed. A method to determine the average radius of curvature of a cellular array was also implemented and is presented here.