Papers by Keyword: Dynamic Strain-Induced Transformation

Abstract: 2-D cellular automaton model was developed to simulate the dynamic strain-induced transformation (DSIT) from austenite (γ) to ferrite (α) and the post-dynamic kinetic behavior in a low carbon steel with the purpose of developing a methodology of mesoscopic computer simulation for an improved understanding of the formation of ultra-fine ferrite (UFF) in DSIT and the conservation of this microstructure during the post-deformation period. The predicted microstructure obtained after DSIT was compared with a quenched dual-phase steel. Its microstructure, consisting of fine-grained ferrite and fine islands of retained austenite dispersed in the matrix, were found to be in good agreement with the predictions. The simulated results indicate that the refinement of ferrite grains produced via DSIT can be interpreted in terms of unsaturated nucleation and limited growth mechanisms. It is also revealed that continuing transformation from retained austenite to ferrite and the reverse transformation both could take place simultaneously during the post-deformation isothermal holding. A competition between them exists at the early stage of the post-dynamic transformation.

Abstract: Plane-strain compression testing on HSLA steel samples using single-pass and multi-pass hot-deformation schedules showed that heavy deformation of metastable austenite below A_e3, developed ultra-fine ferrite grains (<3 µm), increased the fraction of high-angle (>15º misorientation) boundaries (>70%), and encouraged the formation of beneficial g-fibre ((ND//<111>) components along with {332}<113> and {554}<225> texture components, minimising the intensity of harmful ‘cube’ texture.

Abstract: The development of ultrafine grained microstructures in steels has received considerable attention in recent times. In many cases the aim is to produce high strength structural steels with minimal alloying. It is well established that for an equiaxed ferrite with a uniform dispersion of second phase, both the strength and toughness will be markedly improved if the grain size can be reduced to 1-2 µm, from the typical range of 5-10 µm. Means of achieving this through dynamic strain induced transformation are examined here, following a brief overview of some of the key issues encountered when attempting to refine the austenite in existing mill configurations. A number of deformation microstructure maps are developed to aid the discussion.