The effect of phase diagram information on modeling peritectic reaction rates

The peritectic transition is an important phenomenon for many ferrous alloys, especially during the continuous casting process. Many defects have been attributed to this high-temperature phase change, including break-outs, longitudinal cracking, and transverse facial cracking. Observations have been made and reported of the shape and rate of advancement of the δ-ferrite/γ-austenite/liquid junction for Fe-C, Fe-Ni, and Fe-Cr-Ni alloys using the high temperature Confocal Scanning Laser Microscope at Carnegie Mellon University. All diffusion control models used to describe this peritectic reaction rate have shown large dependencies on phase diagram information - namely, the liquidus, solidus, and solvus curves as well as the size of the two-phase ferrite/austenite and austenite/liquid fields. An investigation of available phase diagrams has been made for the Fe-Co system. The effect of diffusivity and phase diagram data on the predicted rate of peritectic reaction was then examined and a contrast against observed rates completed. It was found that the observed results were best predicted utilizing the Bosze and Trivedi diffusion control model with the measured phase diagram points of Harris and Hume-Rothery as an input and a diffusion co-efficient of 3.3 × 10 ^-9 m ² s ^-1.