Abstract
A technique has been developed which allows the rapid quenching of liquid/solid metal slurries directly onto a copper anvil. The quenched ‘liquid’ so produced is very suitable for reliable probe microanalysis, and quenching artefacts which have often bedevilled previous attempts to obtain accurate chemical analyses of the liquid are virtually eliminated. In the present work Fe-Cr-C alloys have been equilibrated at temperatures within the solid/liquid region. and rapidly quenched. The effect of equilibration time and particle size on the carbon and chromium composition of the solid phase has been studied by probe microanalysis on these specimens. Reliable equilibrium values of chromium and carbon in solid and liquid have been measured for a range of alloy compositions (up to 2%C and 20%Cr) and temperatures, and equilibrium partition coefficients k 0 for both chromium and carbon between solid and liquid have been derived. These results indicate an unexpectedly high value of k 0 for carbon in austenite/liquid in the presence of chromium, and confirm the higher values of k 0 for chromium which have been reported. The freezing range for these alloys is believed to be significantly smaller than anticipated, perhaps only 11°C for Fe-1½%Cr-1%C. Small crucibles containing Fe-1½%Cr-1%C alloy were also equilibrated in the solid/liquid region, water quenched, and examined. These specimens were shown to give misleading results due to equilibrium not being fully established. The conditions necessary for obtaining reliable equilibrium compositions in liquid and solid phases by the technique of equilibration, quenching, and analysis are discussed.
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