Opening previously impossible avenues for phase transformation in innovative steels by atom probe tomography

Abstract

After decades of debate on the mechanism for the formation of bainite, it is accepted that bainite grows via a displacive mechanism, i.e. as plate shaped transformation products exhibiting an invariant plane strain surface relief effect. But there is still much discussion on the diffusion or diffusionless nature of bainite. The purpose of this atom probe tomography study was to track the atom distributions during the bainite reaction in steels with different carbon and silicon contents. The steels were transformed over a wide range of temperatures (200–525°C) to elucidate the role of reaction rate and diffusion in the formation of bainite with and without cementite precipitation.