13. Diagram determination methods

Several techniques are used to determine equilibrium diagrams.

• Thermal analysis, with recording of cooling curves, and the more precise differential thermal analysis are often used to determine transformation point temperatures. As these are very much affected by impurities, by supercooling and, more generally, by the delay in transformations that alloys can present, we generally retain the highest temperature among the results proposed by different authors, or obtained during different tests for the same alloy. This is particularly the case for liquidus temperatures. Historically, thermal analysis was the first method used to determine phase equilibria. In 1829, Rudberg first studied phase equilibria in Pb-Sn alloys in Sweden.

• Dilatometry and resistivity measurements can often provide...