Abstract
The potential of three novel processing routes for producing ultrafine ferrite in steel has been investigated. Transformational grain refinement (TGR) from a refined austenite grain size, using heavy, single pass rolling reductions above the Ar 3 temperature produced submicrometre grains in surface layers and 1·5 µm grains in the centre of 2–3·5 mm thick plates of a niobium microalloyed low carbon steel. Cold rolling and recrystallisation of plates prerefined by TGR resulted in submicrometre grains throughout the thickness of 1 mm thick strip. Equal channel angular extrusion of a titanium interstitial free steel at 500°C to an effective strain of 10 produced elongated grains 0·8 × 0·2 μm in size. These processing routes are suitable for producing samples for detailed investigation of the properties of ultrafine ferrite.
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