Ultra Fine Grained Steels

This book discusses results of the New Generation Iron and Steel Materials research project funded over the last ten years. It thoroughly describes theoretical achievements in ultra-fine grain steel and its refinement. It also discusses progress in related areas of engineering and technology. The author has been engaged in the research of new generation structural materials for the last twelve years being Chief Scientist of three national research programs in China.

This book discusses results of the New Generation Iron and Steel Materials research project funded over the last ten years. It thoroughly describes theoretical achievements in ultra-fine grain steel and its refinement. It also discusses progress in related areas of engineering and technology. The author has been engaged in the research of new generation structural materials for the last twelve years being Chief Scientist of three national research programs in China.

In this book, advanced steel technologies mainly developed at the National Institute for Materials Science (NIMS), Japan, for structure control, mechanical properties, and the related mechanisms are introduced and discussed. NIMS has long worked on developing advanced steel techniques, namely, producing advanced steels by using only simple alloying elements such as carbon, manganese, and silicon, and also by utilizing steel scrap. The hope is that this approach will lead to a technology of a so-called steel-to-steel recycling process, with the ultimate goal of a recycling process such as an automotive-steel-to-automotive-steel recycling process to take the place of the current cascade-type recycling system. The main idea is to utilize ultra-grain refining structures and hetero structures as well as martensite structures. In particular, the focus of this book is on tensile strength and toughness of advanced steels from both the fundamental and engineering points of view. Fundamentally, a unique approach to analysis is taken, based on fracture surface energy as effective grain size is employed to better understand the mechanism of property improvement. From the engineering point of view, in fracture toughness such factors as crack tip opening displacement (CTOD) of advanced steels are evaluated in comparison with those of conventional steels.

In recent years, both the steelmaking industry and laboratories in different parts of the world, have shown an increasing interest in reaching an industrial-level production of ultrafine grained steels (also known as ultrafine ferrite), which have a grain size d lower than 5 μm, and enhanced mechanical resistance and fracture toughness. At room temperature, the capacity of the material to be deformed during bending or drawing operations (typical of requirements for automotive parts applications) depends on the interaction of a hard and a soft phase in the microstructure. On the other hand, at high temperatures, these steels may show superplastic behavior if deformed at a precise combination of temperature and strain rate.

This book is a printed edition of the Special Issue "Ultrafine-grained Metals" that was published in Metals

Proceedings of a symposium sponsored by the Shaping and Forming Committee of the Materials Processing and Manufacturing Division (MPMD) and the Mechanical Behavior Committee (Jt. SMD/ASM-MSCTS) of the Structural Materials Division (SMD) of TMS (The Minerals, Metals & Materials Society) and held during the 2002 TMS Annual Meeting in Seattle, Washington February 17-21,2002.

These proceedings of the "Second International Conference on Nanomaterials by Severe Plastic Deformation" review the enormous scientific avalanche that has been developing in the field over recent years. A valuable resource for any scientist and engineer working in this emerging field of nanotechnology.