Understanding Strength-Toughness Combination in the Processing of Engineering Steels: A Perspective

Abstract

High strength-high toughness combination and formability has been the primary focus of the author's research over the last two decades, where the attempt was to either develop newer steels or maximize the fracture resistance of engineering steels at specified levels of strength. In this regard, significant success was achieved based on an extended program of basic research at the author's current and former institutions to understand the part played by crystal structure, solute additions, grain size, grain boundary chemistry, texture, and substructural features such as retained austenite, martensite lath, and packet size, and characteristics of other microstructural constituents. Each of these features influences the fracture mode, the degree of plasticity, and the rate of growth of nucleated voids. Important instances include maraging steels, precipitation hardened stainless steels, low alloy steels, interstitial-free steels, microalloyed steels, pipeline steels, and silicon-containing medium carbon steels. Underlying the attempt to maximize toughness through the study of determining role of microstructure were the development of concept of grain boundary segregation maps, application of stereological approach, new alloy design with lean chemistry, and streamlining of processing-related variables. The aforementioned instances of engineering steels provided a means of comprehensively analyzing the relationship of toughness to microstructural features and facilitate the development of high performance steels.

Keywords:

• Formability
• High strength steel
• Microalloying
• Microstructure
• Toughness

ACKNOWLEDGMENTS

The author gratefully acknowledges a number of friends, colleagues, and their respective institutions in India, United States, Brazil, Canada, United Kingdom, Germany, Netherlands, Finland, and Korea with whom the author interacted and collaborated during the past two decades. Many of them have directly or indirectly contributed to the work described here. In view of a long list of contributors and participants, the author preferred to defer the listing. Every attempt was made to cite relevant references to the described work and any omission is unintentional. It is, however, relevant to acknowledge the most recent support of 2008, received from National Science Foundation (CMMI: 0757799), USA.