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The production of ultrafine ferrite during hot torsion testing of a 0.11 Wt Pct C steel

journal contribution
posted on 2002-09-01, 00:00 authored by P Hurley, B Muddle, Peter HodgsonPeter Hodgson
Ultrafine ferrite grain sizes were produced in a 0.11C-1.6Mn-0.2Si steel by torsion testing isothermally at 675 °C after air cooling from 1250 °C. The ferrite was observed to form intragranularly beyond a von Mises equivalent tensile strain of approximately 0.7 to 0.8 and the number fraction of intragranular ferrite grains continued to increase as the strain level increased. Ferrite nucleated to form parallel and closely spaced linear arrays or “rafts” of many discrete ultrafine ferrite grains. It is shown that ferrite nucleates during deformation on defects developed within the austenite parallel to the macroscopic shear direction (i.e., dynamic strain-induced transformation). A model austenitic Ni-30Fe alloy was used to study the substructure developed in the austenite under similar test conditions as that used to induce intragranular ferrite in the steel. It is shown that the most prevalent features developed during testing are microbands. It is proposed that high-energy jogged regions surrounding intersecting microbands provide potential sites for ferrite nucleation at lower strains, while at higher strains, the walls of the microbands may also act as nucleation sites.

History

Journal

Metallurgical and materials transactions. A, Physical metallurgy and materials science

Volume

33

Issue

9

Pagination

2985 - 2993

Publisher

ASM International

Location

Warrendale, Pa.

ISSN

1073-5623

eISSN

1543-1940

Language

eng

Publication classification

C1 Refereed article in a scholarly journal

Copyright notice

2007, Springer