Formation of uniformly fine grained ferrite structure through multidirectional deformation

The grain size of ferrite transformed from deformed and unrecrystallised au stenite becomes finer as the plastic strain induced in the austenite increa ses. A multidirectional deformation has been proposed as a method for intro ducing a large plastic strain widely in a specimen. The introduced plastic strain was evaluated using an explicit three-dimensional finite element tec hnique, and a spread of the large plastic strain was predicted for unidirec tional compression and bidirectional compression, respectively. A multidire ction deformation thermomechanical treatment simulator was used to verify t he effect of bidirectional compression with regards to the creation of a fi ne ferrite grain structure, as predicted by the finite element analysis. Th e microstructure of the unrecrystallised austenite region after unidirectio nal 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 tha t produced by unidirectional compression. Multidirectional deformation can be applied to obtain ultrafine grain structure for thick products of steels .