About Equilibrium Mode Ruling Ferritic Transformation in Low-Alloy SGI

GARCÍA, LAURA NOEL; CARAZO, FERNANDO DIEGO; BOERI, ROBERTO ENRIQUE

METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE

SPRINGER

Lugar: Berlin; Año: 2019 vol. 50 p. 5585 - 5593

1073-5623

Ferrite precipitating around the graphite nodules shaping the typical bull?s-eye microstructurecould grow under negligible partitioning local equilibrium or under paraequilibrium conditions,as both imply that ferrite inherits the composition of the parent austenite. The first mechanismhas been rejected by other researchers by means of simple calculations of the silicon spike widthnecessary for local equilibrium conditions to take place. Nevertheless, experimental analyses arenecessary to verify this conclusion. In this study, transmission electron microscopy has beenused to assess the presence of a silicon spike in front of the growing ferrite interface. Theoutcome allowed the authors to confirm that a paraequilibrium mode governs the transformation,supporting the conclusions of previous calculations. In addition, some issues aboutferrite growth modeling are discussed.