Austempering of low manganese ductile irons. II: Influence of austenitising temperature

TLDR: In this article, X-ray diffraction, optical microscopy, and hardness measurements were used to determine the austenitising kinetics and the stage I and stage II austempering kinetics of a low Mn, Cu iron and a low Ni-Cu iron.

Abstract: X-ray diffraction, optical microscopy, and hardness measurements were used to determine the austenitising kinetics and the stage I and stage II austempering kinetics of a low Mn, Cu iron and a low Mn, Ni-Cu iron during austempering at 300, 370, and 440 o C after austenitising at 900, 950, and 1000 o C. The study of the austenitising kinetics shows that 60 min is sufficient time to produce a constant C austenite content and that the kinetics are influenced strongly by the volume fraction of pearlite in the structure to be austenitised. Decreasing the austenitising temperature is shown to increase the driving force for the stage I reaction but to have only a small effect on the stage II kinetics