AHSS: Development of High Strength, High Toughness Bainitic Steel

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The primary focus of this research proposal is on creation of high strength, high toughness bainitic steel with extremely fine scale microstructure consisting of bainitic ferrite and austenite. This will be achieved by applying a novel two step austempering process in a high carbon high silicon steel. The basic approach is to create extremely fine grain microstructure consisting of two ductile phases (ferrite andaustenite) by a detailed phase transformation study. This extremely fine scale microstructure will result in simultaneous high yield strength, fatigue strength and fracture toughness. Currently such combination of properties is not available in any structural steel.Intellectual MeritThe intellectual merit of this proposal lies in the fact that it will establish whether a two step austempering process will lead to large super cooling and carbon partitioning, and this leading to extremely fine scale bainitic ferrite and carbon stabilized austenite. Moreover, it will validate whether such a microstructure will impart the desired combination of mechanical properties i.e. simultaneous high yield strength, fatigue strength, fracture toughness and impact strength. This study will also generate significant knowledge base in bainitic transformations in steel.Broad ImpactIf the project is successful, the broad impact of the project will be significant in materials processing and manufacturing industries since it will pioneer a totally new and novel material processing technique for steel and ductile cast irons. This will lead to high-reliability, low cost engineering materials with greater durability. Furthermore, it will generate a new class of structural materials with unique combination of properties (simultaneous high yield strength, fatigue strength, fracture toughness and impact strength). This novel steel will make the structural components lighter, more energy efficient and consequently improve fuel economy and reduce pollution. The austempering process is a more energy efficient heat treatment process since no post heat treatment after quenching is required. Therefore, this process will lead to significant energy savings.