Design of high strength microstructures in carbon steel by thermo mechanical treatment

This research work describes a thermo mechanical investigation of medium carbon steel in the (alpha + gamma) phase region. The aim is to develop a high tensile, ductile microstructure that could have a wide range of engineering applications. Recent advances in the area of crystallographic transformations, especially, precipitation and recrystallization mechanisms, provide strong background to this study. In a preliminary heat treatment, various microstructures (normalized)(p), martensitic(m) and tempered martensite(T)) were produced and deformed to varying degrees. Subsequently, these microstructures were subjected to various intercritical temperatures (740°C 760°C, 780°C) for various times and a very high cooling rate. Light - and transmission electron microscopic investigations were carried out to study the ensuing microstructures. Mechanical testing results (tensile and hardness values) were used to characterize the structures obtained. On analysis of the result, it was observed that well defined microduplex structures of perlitic and martensitic nature, possessing good combinations of strength and ductility, were obtained.