High Strength and High Ductility Martensitic Steels

钢的“马氏体相”非常强，但以变形能力差而臭名昭著。有零星的证据表明，某些形式的马氏体可能具有延展性，但提高延性的机制尚不清楚。延性马氏体可以满足工业和政府对汽车和其他交通工具以及许多核、航空和石化应用的高强度高延性钢的长期需求。该项目有可能极大地推动高强度和延性马氏体钢的设计和发现。本项目选择了一种在石油化工和核工业中应用广泛的改性9%铬-1%钼钢作为试验材料。首席调查员(PI)最近的研究表明，这种钢中可能存在延性马氏体。PIS有着悠久的合作历史，他们在加工和显微/纳米机械方面的专业知识具有很好的互补性。研究生将参观洛斯阿拉莫斯国家实验室的集成纳米技术中心(CINT)，以访问他们先进的显微镜设备。从这个项目中获得的知识将被纳入德克萨斯农工大学和普渡大学的课程。私人投资机构将努力通过德克萨斯农工大学的博士课程以及周边的少数民族院校招收少数民族研究生。技术摘要本项目的目标是从根本上了解合金化学、显微组织和热机械处理(TMT)对延性马氏体钢性能的影响。长期目标是在铁素体/马氏体(F/M)钢中实现高强度和高拉伸塑性。为了实现这一目标，PIS将完成以下任务：(1)采用淬火-分配(Q-P)方法调节马氏体中的碳浓度并控制残余奥氏体的体积分数；(2)将TMT(包括热轧和等通道转角挤压)与Q-P方法相结合，实现细化晶粒和控制马氏体形态；(3)研究T91钢中残余奥氏体膜对变形机制的影响。利用微柱压缩实验研究了沿奥氏体/马氏体界面上的剪切响应，以了解其对F/M钢塑性的影响。此外，他们将在透射电子显微镜中使用原位纳米压痕和原位中子散射(在能源部国家实验室通过一个用户项目)来研究变形过程中奥氏体/马氏体界面对马氏体中位错吸收的影响。一个成功的项目将使延性马氏体钢的机械性能远远超过当今可用的先进结构钢的设计。

Nontechnical AbstractThe "martensite" phase of steel is very strong, but is notorious for poor deformability. There is scattered evidence that shows certain forms of martensite may be ductile, but the mechanisms of enhanced ductility are unclear. Ductile martensite could satisfy a long term industry and government need for high-strength high-ductility steel for automobiles and other transportation vehicles, and a host of nuclear, aerospace and petrochemical applications. This project has the potential to significantly advance the design and discovery of high strength and ductile martensitic steels. In this project, a modified 9% Chromium-1% Molybdenum steel is selected as the test material because it has broad applications in the petrochemical and nuclear industries. The Principal Investigators' (PI's) recent studies show ductile martensite may exist in this steel. The PIs have long lasting history of collaboration and their expertise on processing and microscopy/nano-mechanics is nicely complementary. Graduate students will visit the Center for Integrated Nanotechnologies (CINT) at Los Alamos National Laboratory to access their advanced microscopy facilities. The knowledge derived from this project will be incorporated into curricula at Texas A&M University and Purdue University. The PIs will endeavor to recruit minority graduate students through the Pathway to Doctoral Program at Texas A&M University, and from surrounding minority institutions. Technical AbstractThe objective of this project is to understand, at a fundamental level, the impact of alloy chemistry, microstructure, and thermo-mechanical treatment (TMT) on the properties of ductile martensitic steel. The long term goal is to accomplish high strength and high tensile ductility in ferritic/martensitic (F/M) steel. To achieve this goal, the PIs will accomplish the following tasks: (1) tailor the carbon concentration in martensite and control the volume fraction of retained austenite by using the quench-partitioning (Q-P) approach; (2) combine TMT (including hot rolling and equal channel angular extrusion) with the Q-P method to achieve grain refinement and control the morphology of the martensite; (3) investigate the influence of retained austenite films on the deformation mechanisms in T91 steel. Micropillar compression experiments will be used to investigate the shearing response along the austenite/martensite interface to understand its role on ductility of F/M steel. In addition, they will use in situ nanoindentation in a transmission electron microscope and in situ neutron scattering (at a DoE National Laboratory through a user project) to study the influence of austenite/martensite interfaces on absorption of dislocations in martensite during deformation. A successful project will enable design of ductile martensitic steels with mechanical properties that far exceed those of advanced structural steels available today.