Microstructural characterisation of the super metals by In-lens scanning electron microscopy

BSE images of 0.3-9Ni steel tempered for 1800 s at 873 K after 90% reduction and after being simply quenched from 1073 K are shown in Fig. 5 It is surprising that ultrafine grain size is retained even after tempering at this temperature, when reverse transformation is utilised. The reason for a better strength-ductility balance for the uhrafine grain steel is under investigation. We are also attempting to expand the application of the spontaneous reverse transformation method to plain carbon steels (Yokota et al, 2001).