High Strength and High Ductility Martensitic Steels

钢的“马氏体”相非常强，但因变形性差而臭名昭著。有零散的证据表明，某些形式的马氏体可能是韧性的，但增强韧性的机制尚不清楚。韧性马氏体可以满足工业和政府对汽车和其他运输工具以及许多核、航空航天和石化应用的高强度高韧性钢的长期需求。该项目有可能大大推进高强度和韧性马氏体钢的设计和发现。本课题选择了一种在石油化工和核工业中具有广泛应用的改性9%Cr-1%Mo钢作为试验材料。 主要研究人员（PI）最近的研究表明，韧性马氏体可能存在于这种钢。PI有着长期的合作历史，他们在加工和显微镜/纳米力学方面的专业知识是很好的互补。研究生将访问中心集成纳米技术（CINT）在洛斯阿拉莫斯国家实验室访问他们先进的显微镜设施。从这个项目中获得的知识将被纳入德克萨斯A M大学和普渡大学的课程。PI将奋进通过德克萨斯州A M大学的博士学位课程以及周围的少数民族机构招募少数民族研究生。技术摘要本项目的目的是了解，在一个基本的水平，合金化学，微观结构和热机械处理（TMT）的韧性马氏体钢的性能的影响。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延展性。 为了实现这一目标，PI将完成以下任务：（1）通过淬火-分配（Q-P）方法定制马氏体中的碳浓度并控制残余奥氏体的体积分数;（2）将TMT与联合收割机相结合，（包括热轧和等径角挤压），实现晶粒细化和马氏体形态控制;（3）研究了残余奥氏体薄膜对T91钢变形机制的影响。微柱压缩实验将用于研究沿着奥氏体/马氏体界面的剪切响应，以了解其对F/M钢塑性的作用。 此外，他们将使用透射电子显微镜中的原位纳米压痕和原位中子散射（在能源部国家实验室通过用户项目）来研究奥氏体/马氏体界面对变形期间马氏体中位错吸收的影响。 一个成功的项目将使设计的韧性马氏体钢的机械性能远远超过那些先进的结构钢今天可用。

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.