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Understanding Dislocation Motion and Plasticity via First Principles Simulations Towards Manufacturing of High Ductility Magnesium Alloys

通过高延展性镁合金制造的第一原理模拟了解位错运动和塑性

基本信息

批准号：
2032483
负责人：
Yantao Shen
金额：
$ 46.92万
依托单位：
Board of Regents, NSHE, obo University of Nevada, Reno
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2020
资助国家：
美国
起止时间：
2020-09-01 至 2024-08-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2032483&HistoricalAwards=false
关键词：
Understanding Dislocation Motion Plasticity via

项目摘要

This grant supports fundamental research that facilitates manufacturing of ductile magnesium alloys. Magnesium alloys are the lightest structural materials and they are desirable for automotive and aerospace applications where improved energy efficiency becomes increasingly crucial. However, the limited room temperature ductility of magnesium alloys poses one of the major challenges to broad engineering application of these materials. Cold processing of magnesium at room temperature results in cracking or fracture. Hence, warm processing at elevated temperatures is typically used for industrial manufacturing, but this increases energy cost. To improve the ductility, expensive rare earth elements have been added to magnesium, but this is undesirable because of the high cost and uncertain availability of rare earths. This research project incorporates computational and experimental studies to search for inexpensive and readily available alloying elements for manufacturing new magnesium alloys with superior ductility. The results obtained from this work enables low-cost manufacturing of magnesium alloys which impacts the US economy and the environment. The project also promotes education of Integrated Computational Materials Engineering principles at undergraduate and graduate levels, as well as diversity by involving women and underrepresented minorities in disciplines of Science, Technology, Engineering and Math.Easy dislocation slip systems on the basal and prismatic planes in magnesium are unable to accommodate strain components along the c-axis of the hexagonal close-packed crystal structure. This leads to the limited ductility of magnesium at room temperature. The pyramidal c+a dislocations are able to accommodate c-axis strains, but their critical resolved shear stresses are one to two orders of magnitude higher than those of prismatic and basal dislocations. Consequently, under conventional deformation conditions, the density of c+a dislocations is insufficient to meet the criterion of strain accommodation. This project integrates first-principles hierarchical high-throughput-screening and experimental studies to identify alloying elements that are able to reduce the energy barrier to nucleation and glide of the c+a dislocations in Mg alloys. This is achieved by calculating through first principles simulations how alloying elements influence the landscape of generalized stacking fault energy which describes the energy barrier to dislocation glide. After suitable candidate elements are identified, magnesium alloys are synthesized by ingot casting. Channel die compression is carried out to fabricate samples with refined grains for tensile and compressive tests to determine their mechanical behavior. Dislocation structures are characterized by transmission electron microscopy. The project provides a new, physics-based strategy to develop novel high ductility magnesium alloys, which can be processed into components of useful shapes by rolling, drawing and stamping.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.

该补助金支持促进韧性镁合金制造的基础研究。镁合金是最轻的结构材料，它们在汽车和航空航天应用中是理想的，在这些应用中，提高能源效率变得越来越重要。然而，镁合金有限的室温延展性对这些材料的广泛工程应用提出了主要挑战之一。镁在室温下的冷加工导致开裂或断裂。因此，在高温下的温加工通常用于工业制造，但这增加了能源成本。为了改善延展性，已经将昂贵的稀土元素添加到镁中，但是由于稀土的高成本和不确定的可用性，这是不期望的。本研究计划结合计算和实验研究，寻找廉价和容易获得的合金元素，用于制造具有上级延展性的新型镁合金。从这项工作中获得的结果使镁合金的低成本制造成为可能，这对美国经济和环境产生了影响。该项目还促进了本科生和研究生阶段的综合计算材料工程原理教育，以及通过让妇女和代表性不足的少数民族参与科学、技术、工程和数学学科的多样性。镁基平面和棱柱平面上的易位错滑移系统无法容纳沿沿着六方密排晶体结构的c轴的应变分量。这导致镁在室温下的延展性有限。金字塔形的c+a位错能够容纳c轴应变，但它们的临界分辨剪应力比棱柱形和基底位错高一到两个数量级。因此，在常规变形条件下，c+a位错密度不足以满足应变调节准则。该项目整合了第一原理、分层、高通量筛选和实验研究，以确定能够降低镁合金中c+a位错成核和滑移能垒的合金元素。这是通过第一原理模拟计算合金元素如何影响广义堆垛层错能的景观，描述了位错滑移的能量障碍。在确定合适的候选元素后，通过铸锭法合成镁合金。进行通道模具压缩以制造具有细化晶粒的样品，用于拉伸和压缩测试以确定其机械行为。位错结构的特征在于透射电子显微镜。该项目提供了一种新的、基于物理学的战略，开发新型高延展性镁合金，这种镁合金可以通过轧制、拉伸和冲压加工成有用形状的部件。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。