Effects of deformation on the decomposition of austenite: Part I—The ferrite reaction

Abstract

The influence of plastic deformation at 550°C in the austenite bay on the subsequent isothermal transformation in the range 600–750°C, of a Cr-Mo-Ni steel (En 24) and a 0.2C–5Cr steel, has been quantitatively assessed. Microscopic examination has revealed directly the increased rates of nucleation and growth of the ferrite and the occurrence of intragranular nucleation. The finer ferrite grain sizes resulting from the deformation are shown to give improved mechanical properties. Thin-foil electron microscopy has allowed a close study of the regions giving rise to ferrite nuclei, and also of the frequent irregular growth in regions of high dislocation density. Using an iron-0.2C-1V alloy, it has been shown that small deformations at temperatures as high as 875°C have a pronounced effect on the subsequent reaction at 700°C.