Ductile 2-GPa steels with hierarchical substructure

• 成果类型: Article
• 署名作者: Li, Yunjie; Yuan, Guo; Li, Linlin; Kang, Jian; Yan, Fengkai; Du, Pengju; Raabe, Dierk; Wang, Guodong
• 署名单位: Northeastern University - China; Chinese Academy of Sciences; Institute of Metal Research, CAS; Max Planck Society
• 刊物名称: SCIENCE
• ISSN/ISSBN: 0036-13749
• DOI: 10.1126/science.add7857
• 发表日期: 2023-01-13
• 页码: 168-173
• 关键词: high-strength steel; medium-mn steel; lath martensite; mechanical-properties; austenite; carbon; sustainability; temperature; plasticity; STABILITY

摘要

Mechanically strong and ductile load-carrying materials are needed in all sectors, from transportation to lightweight design to safe infrastructure. Yet, a grand challenge is to unify both features in one material. We show that a plain medium-manganese steel can be processed to have a tensile strength >2.2 gigapascals at a uniform elongation >20%. This requires a combination of multiple transversal forging, cryogenic treatment, and tempering steps. A hierarchical microstructure that consists of laminated and twofold topologically aligned martensite with finely dispersed retained austenite simultaneously activates multiple micromechanisms to strengthen and ductilize the material. The dislocation slip in the well-organized martensite and the gradual deformation-stimulated phase transformation synergistically produce the high ductility. Our nanostructure design strategy produces 2 gigapascal-strength and yet ductile steels that have attractive composition and the potential to be produced at large industrial scales.