Abstract
The grain size of ferrite transformed from deformed and unrecrystallised austenite becomes finer as the plastic strain induced in the austenite increases. A multidirectional deformation has been proposed as a method for introducing a large plastic strain widely in a specimen. The introduced plastic strain was evaluated using an explicit three-dimensional finite element technique, and a spread of the large plastic strain was predicted for unidirectional compression and bidirectional compression, respectively. A multidirection deformation thermomechanical treatment simulator was used to verify the effect of bidirectional compression with regards to the creation of a fine ferrite grain structure, as predicted by the finite element analysis. The microstructure of the unrecrystallised austenite region after unidirectional and bidirectional compressions was investigated for a Fe-0.16C-0.4Si-1.4Mn wt- steel. The uniformly fine grained ferrite structure produced by the bidirectional compression covered a wider region in comparison with that produced by unidirectional compression. Multidirectional deformation can be applied to obtain ultrafine grain structure for thick products of steels.
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