Formation process of ultrafine grained ferrite through a simple thermomechanical route composed of cold-rolling and annealing of dual-phase starting microstructures was investigated. A 0·1C steel having a ferrite–martensite dual-phase microstructure was cold-rolled by 91 and subsequently annealed below the eutectoid (A1) temperature. During the annealing, the cold-rolled microstructure gradually changed to be equiaxed ultrafine ferrite, without preferential growth of particular ferrite grains. Hardness of the cold-rolled specimen continuously decreased without a significant drop. The main components of texture in the cold-rolled specimen, α-fibre and γ-fibre, did not change greatly after the formation of ultrafine grains. It was suggested that finely subdivided region having large misorientations in the cold-rolled state grew with recovery to form the ultrafine ferrite.
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