In Situ Neutron Diffraction and Fluid Dynamics Modeling of Dynamic Recrystallization in Mg Alloys

镁合金动态再结晶的原位中子衍射和流体动力学模拟

• 批准号: 1308548
• 负责人: Hahn Choo
• 金额: $ 35.24万
• 依托单位: University of Tennessee Knoxville
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-06-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1308548&HistoricalAwards=false
• 关键词: Situ; Neutron; Diffraction; Fluid; Dynamics

TECHNICAL SUMMARY:The objective of this project is to investigate the underlying physics of dynamic recrystallization in magnesium alloys during severe plastic deformation at elevated temperatures. Dynamic recrystallization involves the creation of new grains with low dislocation densities in a deformed microstructure during deformation. Dynamic recrystallization can strongly influence the mechanical properties in the variety of wrought metals and alloys used for structural applications. Friction-stir processing will be used to produce large plastic strains in specimens of commercial magnesium alloy AZ31. The transient nature of dynamic recrystallization and the critical role that twinning plays on grain refinement and crystallographic texture development in this magnesium alloy will be studied using in-situ, real-time neutron and synchrotron X-ray diffraction measurements and computational fluid dynamics (CFD) modeling. The research consists of three primary tasks: (1) develop a portable friction-stir-processing machine for use in in-situ diffraction studies; (2) in-situ, real-time diffraction measurements during plastic deformation to study the transient evolution of microstructure, namely texture, internal strain, dislocation density, subgrain size and twin density; and (3) computational fluid dynamics simulation of plastic deformation to study material flow rate and flow patterns in reference to temperature distribution and evolution. Simulation predictions will be correlated to microstructure evolution data to identify the dynamic recrystallization mechanisms responsible for microstructure development. Education, training and outreach activities will include high-school, undergraduate and graduate students. A new course on neutron diffraction will be developed.NON-TECHNICAL SUMMARY:Dynamic recrystallization is a complex phenomenon that occurs in metals and alloys while they are deformed, usually at elevated temperatures. It can significantly change the microstructure and properties of a material, either detrimentally or advantageously. The objective of this project is to investigate the mechanisms by which dynamic recrystallization occurs. This research will incorporate a magnesium alloy, AZ31, of interest for light-weighting vehicles. It will also use friction stir processing, which is of interest for advanced manufacturing. These will be combined with advanced diffraction experiments to study the underlying mechanisms of dynamic recrystallization. Education, training and outreach activities will include high-school, undergraduate and graduate students. A new course on neutron diffraction will be developed.

技术概述：本项目的目的是研究镁合金在高温下剧烈塑性变形时动态再结晶的基本物理现象。动态再结晶涉及在变形过程中在变形的微观结构中产生具有低位错密度的新晶粒。动态再结晶可以强烈地影响各种用于结构应用的锻造金属和合金的机械性能。搅拌摩擦处理将用于生产大塑性应变的商品镁合金AZ31试样。通过现场实时中子和同步加速器x射线衍射测量和计算流体动力学（CFD）建模，研究动态再结晶的瞬态性质以及孪晶在镁合金晶粒细化和晶体织构发展中的关键作用。该研究包括三个主要任务：(1)开发用于原位衍射研究的便携式摩擦搅拌处理机；(2)在塑性变形过程中进行原位、实时衍射测量，研究微观组织织构、内部应变、位错密度、亚晶粒尺寸和孪晶密度的瞬态演变；(3)计算流体力学模拟塑性变形，研究参考温度分布和演化的物质流动速率和流动模式。模拟预测将与微观组织演变数据相关联，以确定负责微观组织发展的动态再结晶机制。教育、培训和拓展活动将包括高中生、本科生和研究生。将开设一门新的中子衍射课程。动态再结晶是发生在金属和合金变形过程中的一种复杂现象，通常在高温下发生。它可以显著改变材料的微观结构和性能，或有利或不利。本项目的目的是研究动态再结晶发生的机制。这项研究将采用一种镁合金AZ31，用于轻型汽车。它还将使用搅拌摩擦加工，这是先进制造的兴趣。这些将与先进的衍射实验相结合，以研究动态再结晶的潜在机制。教育、培训和拓展活动将包括高中生、本科生和研究生。将开设一门新的中子衍射课程。