Processing Opportunities for New Advanced High-Strength Sheet Steels

Currently there is considerable interest in developments leading to new advanced high-strength sheet steels (AHSS) for automotive and other transportation applications that demand high strength, light weight materials. Design requirements will involve material properties with strengths greater than currently available dual phase and transformation-induced plasticity (TRIP) steels (steels in this group are referred to as the oFirst Generationo of AHSS), with good ductility and formability, but produced at a cost less than the high ductility stainless steels or high manganese TWIP steels (materials referred to as the oSecond Generationo of AHSS). Recent studies have shown that materials that satisfy the required property/cost combinations will include complex microstructures containing high amounts of retained austenite in combination with a high strength constituent that may be ultrafine grained ferrite, martensite, bainite, and/or combinations of ferrite-based constituents. In this article, selected methodologies leading to the production of new AHSS materials will be reviewed and assessed to provide a framework for consideration of new concepts and processing routes that will be required in production operations.