Fast estimation of the phase diagram of a binary system using infrared thermography

Abstract

Arial, 9pt, bold) A method based on infrared thermography for fast estimation of the phase diagram of solid-liquid binary systems has been developed. The method involves heating simultaneously a set of small crystals of a system A/B, with compositions ranging from 0%B/(A+B) to 100%B/(A+B), and to observe their thermal behavior with an infrared camera. Recorded data are then analyzed by Singular Value Decomposition techniques to identify liquidus and solidus lines. Different binary systems has been investigated and the results achieved have been compared with the phase diagrams determined by standard DSC testing, as well as with the phase diagrams predicted by thermodynamic modeling. The proposed method aims at providing an approximate, but accurate enough estimation of the phase diagram of binary systems. The method involves heating simultaneously a set of small samples of a system A/B, with compositions ranging from 0%B/(A+B) to 100%B/(A+B), and to observe their thermal/optical evolution with an infrared camera. Recorded data are then analyzed to identify points of equilibrium between solid and liquid phases of each sample. Accordingly, main elements of the experimental set-up are the infrared camera, the sample-set and the heating system. The sample-set consist of a series of small crystals (~2-4 mm in diameter) of the binary system to be tested placed in a more or less regular manner on the surface of a thin plate. The plate is made of aluminum with highly polished faces so as to have low surface's emissivity in the infrared. The composition of the samples ranges from 0%B/(A+B) to 100%B/(A+B), with a pitch of 2-5% most times. The sample-set is put on the heating system of the experimental set-up, and it is submitted to a constant heating rate up to