Advanced High Strength Multiphase Steels through a Combined Alloy-Microstructural Design

在接下来的几年里，联邦政府将实施美国最全面的改革。S.车队？的排放和燃油经济性标准。提高燃油经济性的最有吸引力的方法之一是汽车？通过使用先进高强度钢（AHSS），可以找到近期和具有成本效益的解决方案。因此，该奖项的研究目标是设计和制造低合金、低成本的多相钢，其复合显微组织由超细晶（UFG）铁素体基体和分散的贝氏体和稳定奥氏体组成。这种显微组织应确保用于减轻重量的高强度、允许容易成形的高延展性和高断裂韧性。这些目标将通过合金和微结构设计的协同组合来实现，所述协同组合经由计算和实验方法，包括合金成分的设计和用于本构相的最佳体积分数的热处理时间表，以及使用热机械加工技术将晶粒尺寸细化到亚微米到纳米范围，所述热机械加工技术包括在新的基于微结构的工艺优化建模。如果成功的话，这项研究的结果将提供一个机会，彻底改变该领域，从目前昂贵的或低延展性和差的成形性HSS，AHSS具有高强度，高延展性，良好的成形性，低成本的组合;并通过创建一个全新的家庭？纳米钢对未来先进的运输工具，发电设备和武器系统都将产生重大影响。最终，在这项工作中开发的合金化和微观结构设计的方法将大大有助于提高美国制造业的竞争力的整体努力。研究生和本科生，包括几个少数民族学生将受益于新的课程开发，课堂教学和直接参与研究。K-12学生和高中教师将参与计算/实验研究活动，以提高他们对科学和工程的认识，并为他们提供第一手的研究经验。

In the next few years, the Federal government will implement the most comprehensive overhaul of the U. S. vehicle fleet?s emission and fuel economy standards to date. One of most attractive approaches to improved fuel economy is vehicle?s weight reduction for which near-term and cost-effective solutions can be found through the use of Advanced High Strength Steels (AHSS). Thus, the research objective of this award is to design and fabricate low-alloy, low-cost multiphase steels with a composite microstructure consisting of an ultrafine-grained (UFG) ferrite matrix with dispersions of bainite and stabilized austenite. Such microstructure should assure high strength for weight reduction, high ductility to allow easy formability, and high fracture toughness. These goals will be achieved through the synergistic combination of alloy and microstructural design via both computational and experimental approaches including design of alloy compositions and heat treatment schedules for optimal volume fractions of the constitutive phases, and refinement of the grain size to submicron to nano range using thermomechanical processing techniques including severe strain path changes and severe simple shear deformation with the help of a novel microstructure based modeling for process optimization. If successful, the results of this research will provide an opportunity for revolutionizing the field, by moving away from current expensive or low ductility and poor formability HSSs, to AHSSs possessing high strength-high ductility-good formability-low cost combination; and by the creation of an entirely new family of ?nano-steels?, which will have significant impact on future advanced transportation vehicles, power generation equipment, and weapons systems. Ultimately, the methodologies for alloying and microstructural design developed in this work will significantly contribute to the overall effort to increase the competitiveness of U.S. manufacturing. Graduate and undergraduate students including several minority students will benefit through new course developments, classroom instruction and direct involvement in the research. K-12 students and high school teachers will be engaged in the computational/experimental research activities to increase the awareness of science and engineering among them and provide them firsthand research experience.