ABSTRACT
In the case of machines and structures, steels often provide the best overall life-time economy, especially in the case of high-strength steels, the use of which conserves raw materials and minimizes energy consumption. This chapter is mainly concerned with transformation to ferrous martensite, which is a basic ingredient in many high-strength steels. The chapter covers the crystallography and morphologies of lath and plate martensite, as well as possible mechanisms of nucleation and growth, in the case of both athermal and thermally activated martensite. The effects of applied stress, plastic strain and magnetic fields on the transformations are explained as are the disordering, segregation and precipitation effects caused by the diffusion of carbon immediately after the formation of martensite and during subsequent tempering. Besides martensite in ferrous systems, details are given of martensite transformations in ordered alloys, where transformation strains are accommodated elastically giving rise to thermoelasticity, superelasticity, shape memory and rubber-like behavior. Case studies are described for advanced high-strength steels, bearing steels and martensitic stainless steels.
