History of Investigations into the Allotropy of Iron

Phase transformations in iron have been studied in detail for the last 140 years. The fundamentals involved - thermodynamics, phase stability, and magnetism - have also been the basis for Prof. David Laughlin's career. In honor of Professor Laughlin, I will present an overview of the the history surrounding the phase stability of α, β, γ, and δ iron. I will also summarize some of the data that has been used to quantify the differences in Gibbs energy between the phases, including both historical data as well as data contained in today's CALPHAD databases.