XRMON-GF Experiments Devoted to the in Situ X-ray Radiographic Observation of Growth Process in Microgravity Conditions

Abstract

Structural material properties are strongly related to the solidified microstructures, thus precise control of microstructural formation and selection are crucial in engineering. 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 the major source of various disturbing effects. Solidification under microgravity conditions is an efficient way to eliminate buoyancy and convection, providing valuable benchmark data for the validation of analytical 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 frameworks of the ESA - MAP programme entitled XRMON, an experimental apparatus has been developed to perform directional and equiaxed 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 the key elements of the XRMON-GF device, and some scientific results achieved during the MASER-12 sounding rocket mission and the 58 th ESA Parabolic flight campaign are finally presented in the third and last part of the paper.