Manufacturing High Strength Nanocrystalline Metal Sheets Using a Cold Angular Rolling Process

几千年来，传统金属加工产生的层状结构的形成一直被用来实现金属的显著强度。例如日本的剑和大马士革的钢铁。目前的制造方法可以通过轧制结合不同的金属来大规模生产层状结构，但机械性能的改善有限。近年来的研究表明，采用高压和机械剪切来细化金属复合材料的显微组织和提高其强度的严重金属变形技术是可行的，但这些技术的非连续性一直是规模化和商业化的障碍。该奖项支持开发连续制造工艺以生产高强度纳米晶体金属薄板所需的基础研究。该项目使用了一种新的冷角轧制工艺，该工艺使用单个辊子在连续过程中剪切和压缩金属，以产生层状纳米晶片。这一工艺的价值在于通过连续、节能的工艺对低成本的板材进行有效的粘接和微观结构修改。该项目提高了美国的金属制造能力，以设计和制造具有优异性能的纳米结构合金，用于需要轻质结构金属的应用，促进科学进步，促进国家繁荣和经济。从事这项研究的大学生正在为在研究实验室和工业中从事先进材料工程和制造工作做准备。有色金属，包括铝和镁合金，具有广泛的工业应用，但它们通常机械强度低，抗疲劳性能差。为了能够广泛使用轻质超细晶金属和合金，迫切需要开发一种连续加工方法来同时结合和细化块体轻合金的组织。该项目采用了一种新的冷转角轧制工艺(CARP)，该工艺将等通道转角挤压和单辊冷轧一步到位，能够生产出没有任何长度限制的层次化纳米晶合金薄板的连续板材。为了进一步改善微观结构和提高材料性能，该项目使用了多层不同金属来结合界面诱导的塑性变形。通过结合CARP、有限元方法以及微观结构和力学性能表征，该项目提供了关于(I)应力-应变状态与微观结构之间的关系，(Ii)界面诱导流动、塑性变形和摩擦材料形成，以及(Iii)层状金属摩擦材料的微观结构和力学性能的新的基本知识。

The formation of layered structures produced by traditional metalworking has been used to achieve significant strengths in metals for thousands of years. Examples are Japanese swords and Damascus steels. Current manufacturing methods can produce layered structures on a large-scale by bonding separate metals through rolling, but with limited improvements in mechanical properties. Recent studies demonstrated the applicability of severe metal deformation techniques, which introduce high pressure and mechanical shearing to refine the microstructure of metal composites and greatly increase their strength, but the non-continuous nature of these techniques has been a barrier to scale-up and commercialization. This award supports fundamental research needed for the development of a continuous manufacturing process to produce high strength nanocrystalline sheet metals. This project uses a new cold angular rolling processing, which employs a single roller for shearing and compressing metals in a continuous process to create layered nanocrystalline sheets. The value of this process comes through efficient bonding and microstructural modification of low-cost sheet metals in a continuous, energy-efficient process. The project increases U.S. metal manufacturing capability to design and manufacture nanostructured alloys with superior properties for applications requiring lightweight structural metals, promoting the progress of science and advancing national prosperity and economy. University students engaged in this research are being prepared for careers in advanced materials engineering and manufacturing in research laboratories and industries.Non-ferrous metals, including aluminum and magnesium alloys, have a broad range of industrial applications, but they typically suffer from low mechanical strength and poor fatigue resistance. To enable broad use of lightweight ultrafine-grained metals and alloys, there is a critical need for the development of a continuous processing method to simultaneous bond and refine the microstructure of bulk lightweight alloys. This project uses a new cold angular rolling process (CARP) which combines equal-channel angular pressing and single-roller cold rolling in a single-step enabling the production of continuous sheets of hierarchically structured, nanocrystalline alloy sheets without any length limitations. To further improve the refinement of the microstructure and increase in material properties, the project uses layers of dissimilar metals to incorporate interface-induced plastic deformation. By combining CARP, finite element method (FEM), and microstructure and mechanical property characterization, the project provides new fundamental knowledge of (i) relationships between stress-strain state and the microstructure, (ii) interface-induced flow, plastic deformation, and tribomaterial formation, and (iii) microstructure and mechanical properties that develop in layered metallic tribomaterials.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.