Abstract: Directional solidification of thin alloy sheets has been studied in-situ by X-radiography using high brilliance synchrotron radiation. Use of a high-resolution, low-noise fast readout detector provided spatial resolutions down to 1.5 microns and temporal resolutions down to 0.15 s, permitting video microscopy of solidification phenomena such as columnar and equiaxed dendrite growth, eutectic and monotectic growth, primarily in aluminium alloys. The results have brought new insight into fields such as mechanisms of dendrite fragmentation, and for droplet formation, hydrodynamically driven coagulation and microstructure formation during monotectic solidification. Image processing can provide in-situ information on important solidification parameters such as crystal morphologies, interface velocities, compositional variations in the melt, and flow fields, and accordingly the method is expected to be of importance in both phenomenological and quantitative validation of microstructure growth models. The video sequences are also particularly useful in teaching solidification.

Citation: Lars Arnberg and Ragnvald H. Mathiesen, "The Real-Time, High-Resolution X-Ray Video Microscopy of Solidification in Aluminum Alloys," JOM, August 2007, pp. 20-26.

Following are supplementary presentations by the authors describing the experimental set-up and mathematical models for thermal and concentration distributions in two of the experiments, along with a PDF of the web-enhanced JOM article.