13. "Study of the austempering transformation kinetics in compacted graphite cast irons"

R. GREGORUTTI; K. LANERI; DESIMONI, J; ROBERTO CARLOS MERCADER

Metallurgical and Materials Transactions A-Physical Metallurgy and Materials Science

Año: 2004 vol. 35 p. 103 - 110

1073-5623

In this work the phases involved in the transformation austenite ® ferrite + high-carbon austenite in cast irons were assessed by means of Mössbauer spectroscopy and hardness measurements for samples austempered at five different temperatures between 573-673K with two Mn contents. The C content in the high-carbon austenite was found to have a dependence of t0.40± 0.05 on the austempering time t, which evidences that diffusion of carbon has taken place. The kinetic parameter k calculated using the JMA equation has a maximum of 3.9x10–3(s-1) at »623K and corroborates that Mn slows down the transformation rate.