CAREER: Towards Room Temperature Formability in Magnesium Alloys

技术：为了应对不断上涨的燃料价格，提高交通工具的燃油经济性，由于镁合金的轻量化特性，人们已经做出了相当大的努力来了解和提高镁合金的结构-性能关系。然而,镁?在室温下的低延展性降低了它的成形性和它在一些减轻重量的应用中的潜力。目前，镁片是在高温下形成的，这大大增加了它们的成本。在过去的100年里，用于汽车车身和封闭的主要材料是冷轧钢，其密度是镁的三倍，但可以更经济地制造。目前镁合金的研究工作主要集中在最大化有限的材料性能，如强度，耐腐蚀和抗蠕变，然而，通过新型增强结构提高镁合金延展性的机制仍然很大程度上未被探索。这个CAREER项目的具体研究目标是通过纳米颗粒增强来提高镁合金的室温延展性。核心假设是金属基体中纳米颗粒的存在会影响镁？S晶粒细化能力和增强塑性变形机制。为了实现这一目标并检验中心假设，本CAREER项目的研究目标是：1)确定微观结构参数（晶粒细化、纳米颗粒尺寸和体积分数）对塑性变形机制的作用和影响：孪生和滑移；2)建立复杂变形机制与纳米颗粒增强六边形封闭填充（HCP）金属（如镁）微观结构之间的新关系；3)制定并验证了基于预测热力学的模型，该模型将加工参数与可成形性优化的微观结构联系起来。长期的研究目标是利用计算热力学方法来制造具有独特增强结构的金属基复合材料，这些结构可以展示出激进的、转化的特性，如自修复、仿生增韧和低温成形性。非技术：PI的中心主题是什么？美国的教育、服务和拓展活动是通过辅导进行的教育。长期教育的目标是使用这种指导方法来提高认识，并进一步发展以社区为中心的工程和科学课程，以培养以用户为中心的解决方案，并在技术上具有重要意义。为达致此目标，本计划的教育目标是：1)透过以社区为中心的设计项目，让工程专业学生了解现代及相关工程解决方案的需要，以满足本地及全球社区的需要；2)整合和利用已建立的部门计划与当地小学计划，以提高教师的信心，同时提高科学能力；3)创建工业和国际合作，为学生和PI提供独特的网络和学习机会。这个综合研究和教育的CAREER项目为当今一些与技术相关的最大社会问题提供了解决方案：1)轻量化车辆以提高燃油效率，以应对燃料和能源价格的快速上涨；2)利用纳米颗粒操纵和控制HCP金属的微观结构，提高成形性；3)为K-12教师提供科学教育计划，提供一种乘法方法来解决更多服务不足和代表性不足的学生的科学教育需求；4)利用创新的指导模式，在技术、分析导向的教育系统中，教育下一代工程师，使他们更广泛地认识和欣赏他们对当地和全球社区的影响。该项目由DMR的金属材料与纳米结构项目和CMMI部门的材料加工与制造项目共同资助。

TECHNICAL: To combat rising fuel prices and increase the fuel economy in transportation vehicles, considerable efforts have been made to understand and enhance the structure-property relationships in magnesium alloys due to their lightweight characteristics. However, magnesium?s low ductility at room temperature reduces its formability and its potential for use in several weight-saving applications. Currently, magnesium sheets are formed at elevated temperatures, dramatically increasing their cost. For the last 100 years, the dominant material used for automotive bodies and closures is cold rolled steel, whose density is three times greater than magnesium but can be manufactured more economically. Current research efforts in magnesium alloys have largely focused on maximizing a limited number of material properties such as strength, corrosion and creep resistance, however, mechanisms for enhancing ductility in magnesium alloys through novel reinforcement structures have remained largely unexplored. The specific research goal of this CAREER project is to increase the room temperature ductility of magnesium alloys through nanoparticle reinforcement. The central hypothesis is that the presence of nanoparticles in the metal matrix can affect magnesium?s grain refining ability and enhance plastic deformation mechanisms. In pursuit of this goal and to test the central hypothesis, the research objectives of this CAREER project are to 1) determine the role and measure the effect of microstructural parameters (grain refinement, nanoparticle size and volume fraction) on plastic deformation mechanisms: twinning and slip; 2) develop new relationships between complex deformation mechanisms and nanoparticle reinforced microstructures of hexagonal closed packed (HCP) metals such as magnesium and 3) formulate and validate a predictive thermodynamics-based model that connects processing parameters to a microstructure optimized for formability. The long-term research goal is to utilize a computational thermodynamics approach to create metal-matrix composites with unique reinforcement structures that can demonstrate radical, transformative properties such as self-healing, biomimetic toughening and low temperature formability. NON-TECHNICAL: The central theme for PI?s education, service and outreach activities is education through coaching. The long-term education goal is to use this coaching methodology to increase the awareness and further the development of a community-centric engineering and science curriculum that fosters solutions that are user-focused as well as technologically significant. To achieve this goal, the education objectives of this project are to 1) expose engineering students, through focused community-centric design projects, to the need for modern and relevant engineering solutions that will meet the needs of both local and global communities; 2) integrate and leverage an established departmental program with a local elementary school program which promotes teacher confidence while improving science competency and 3) create industrial and international collaborations to provide unique networking and learning opportunities for the students and PI. This integrated research and education CAREER project provides solutions to some of the greatest technologically relevant societal issues today: 1) light-weighting vehicles to increase fuel efficiency in order to counter the rapidly rising price of fuel and energy; 2) utilizing nanoparticles to manipulate and control the microstructure of HCP metals for enhanced formability; 3) a science education program for K-12 teachers that provides a multiplicative approach to addressing the science education needs of a greater number of under-served and under-represented students and 4) utilizing an innovative coaching model to educate the next generation of engineers with a broader awareness and appreciation of their impact on local- and global- communities in a technical, analytically-oriented education system.This project is being jointly funded by the Metallic Materials & Nanostructures program in DMR and the Materials Processing & Manufacturing program in CMMI Division.