PREDICTION OF MICROSTRUCTURAL STATES IN CR-MO STEELS USING PHASE EVOLUTION DIAGRAMS

The present paper introduces a new concept of phase evolution diagram and demonstrates its utility in predicting the subsequent microstructu ral states and assessing the previous thermal history, based only on t he information of the composition of the parent matrix. The phase evol ution diagram depicts the time variation of the solute composition of the parent proeutectoid ferrite matrix. The different metastable phase fields which evolve as a consequence of the variation in the solute c omposition are also superimposed in the diagram. The phase evolution d iagram is constructed based on the extensive analytical electron micro scopy studies on the precipitation of secondary carbides in Cr-Mo stee ls. The paper discusses the underlying principle, details of evaluatio n of the required experimental data and usefulness of the phase evolut ion diagram.