GOALI: Friction Stir Joining of Bulk Metallic Glasses and Their Composites

块体金属玻璃是一类相对较新的工程材料，具有优异的性能和独特的加工能力。它们的高强度、弹性、耐腐蚀性和软磁特性使其在一系列军事、医疗、体育和工业应用中具有吸引力。然而，金属玻璃的连接在多个长度尺度上仍然是一个重大挑战。这项GOALI学术联络机会(GOALI)研究将使用固态连接方法来获得具有优异表面特性的大块金属玻璃。将这些结构用作生物植入物可能会减少组织炎症、骨骼退化和置换手术的可能性，从而促进国民健康和福利。在装甲车辆和航天器上使用叠层金属玻璃作为穿透盾牌，防止轨道碎片撞击，将极大地促进国防利益。拟议的项目将在许多方面进行合作，学术界和产业界合作伙伴积极参与，包括为该项目资助的两名研究生提供行业实习机会。它将为学生提供一个难得的机会，将课堂概念与产业研究和开发相结合。该项目将吸引来自代表性不足群体的学生，并将有助于培养先进制造业的下一代科学家/工程师。该项目还将使K-12的学生和教师接触到新兴的科学技术领域，从而造福社会。该项目的研究目标是通过集成的实验和建模方法，实现对非晶态金属合金及其复合材料的搅拌摩擦连接过程的基本科学理解。该研究项目将建立在有希望的初步实验的基础上，以了解搅拌摩擦连接过程中相邻层中的材料流动、多尺度变形行为、分子动力学模拟和大型有限元建模。拟议工作产生的独特和基础性的科学贡献将是四方面的。首先，该研究将促进对非晶态金属和复合材料在高应变加工过程中剪切混合和冶金结合形成的认识。其次，它将使人们能够理解不同微观结构特征相互作用所产生的变形机制。第三部分涉及原子尺度模型，它将创造出响应高应变的自由体积演化的技术诀窍。最后，建议的研究将有助于开发一个框架来预测位置特定的属性，包括根据温度、降温速度和应变分布的空间分辨结构演化。拟议研究的主要创新在于实现了非晶态金属的均质和堆积结构，这是现有技术无法实现的，该技术假设非晶态金属成分之间的强烈剪切混合会破坏表面氧化物，导致原始金属流动和冶金结合。加工过程中的高应变预计会增加金属玻璃中原子尺度的不均匀性，导致返老还童，并与铸造非晶态结构相比显著改善机械性能。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Bulk metallic glasses are a relatively new class of engineering materials with a combination of exceptional properties and unique processing ability. Their high strength, elasticity, corrosion resistance and soft magnetic properties make them attractive for a range of military, medical, sporting, and industrial applications. However, joining of metallic glasses remains a major challenge across multiple length-scales. This Grant Opportunity for Academic Liaison with Industry (GOALI) research will use a solid-state joining approach to achieve large sections of bulk metallic glasses with superior surface properties. Use of these structures as bio-implants could potentially lessen the likelihood of tissue inflammation, bone deterioration and replacement surgeries thus advancing national health and welfare. Use of stacked metallic glasses as penetrator shields on armor vehicles and spacecraft protection against orbital debris impacts will significantly advance the national defense interests. The proposed project will be collaborative in many aspects, with active engagement between the academic and industrial partners, including an industry internship for two graduate students funded by the project. It will provide a rare opportunity for students to integrate classroom concepts with industrial research and development. The project will engage students from underrepresented groups and will contribute to educating the next generation of scientists/engineers in advanced manufacturing. The project will also benefit society by exposing K-12 students and teachers to emerging areas in science and technology.The research objective of this GOALI project is to achieve fundamental scientific understanding of friction stir joining process for amorphous metallic alloys and their composites by an integrated experimental and modeling approach. The research project will build on promising preliminary experiments to connect the understanding of material flow in adjoining layers during friction stir joining process, multi-scale deformation behavior, molecular dynamics simulations, and large-scale finite element modeling. The unique and fundamental scientific contributions resulting from the proposed work will be four fold. Firstly, the research will advance knowledge of shear mixing and metallurgical bond formation during high strain processing of amorphous metals and composites. Secondly, it will enable understanding of deformation mechanisms resulting from the interaction of different microstructural features. Third part involving atomistic-scale models will create knowhow on free volume evolution in response to high strain. Lastly, the proposed research will help in the development of a framework to predict location specific properties consisting of spatially resolved structure evolution from the temperature, cooling rate, and strain distribution. The main innovation of the proposed research lies in achieving homogeneous and stacked structures of amorphous metals that are unattainable using existing technologies with the hypothesis that intense shear mixing at the interface between amorphous metallic components ruptures the surface oxide resulting in pristine metal flow and metallurgical bonding. The high strain during processing is expected to increase atomic-scale inhomogeneity in metallic glasses leading to rejuvenation and markedly improved mechanical properties compared to cast amorphous structures.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.