Investigation of gravity effects on solidification of binary alloys with in situ X-ray radiography on earth and in microgravity environment

Abstract

As most of the phenomena involved during solidification are dynamic, in situ and real-time X-ray imaging should be retained as the method of choice for investigating the solidification front evolution of metallic alloys grown from the melt. On Earth, natural convection in the melt is well known to be the major source of various disturbing effects which can significantly modify or mask important physical mechanisms. Microgravity environment is an efficient way to eliminate buoyancy and convection to provide benchmark data for the validation of models and numerical simulations. In addition, a comparative study of solidification experiments carried out on Earth and in space can also enlighten the effects of gravity. In the frame of the ESA - MAP programme entitled XRMON, an experimental set-up has been developed to perform directional solidification in microgravity conditions with in situ X-ray radiography observation. In the first part of this paper, we will present a brief review of some effects induced by gravity on the solidification process and investigated by mean of synchrotron X-ray radiography at ESRF (European Synchrotron Radiation Facility). In the second part of this paper, we will describe some results obtained with a prototype of the XRMON-Gradient Furnace set-up. These preliminary results show the large capabilities of the experimental set-up in terms of thermal behaviour, as well as X-ray observation.