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

块体非晶合金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。其高强度、弹性、耐腐蚀性和软磁性能使其在军事、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。这个学术界与工业界联络（GOALI）研究的资助机会将使用固态连接方法来实现具有上级表面性能的大块金属玻璃。使用这些结构作为生物植入物可能会减少组织炎症、骨退化和置换手术的可能性，从而促进国民健康和福利。使用叠层金属玻璃作为装甲车辆的穿甲防护层和防止轨道碎片撞击的航天器防护层，将大大提高国防利益。拟议的项目将在许多方面进行合作，学术和工业合作伙伴之间的积极参与，包括由该项目资助的两名研究生的行业实习。它将为学生提供一个难得的机会，将课堂概念与工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，并将有助于教育先进制造业的下一代科学家/工程师。该项目还将通过让K-12学生和教师接触新兴的科学和技术领域来造福社会。该GOALI项目的研究目标是通过综合实验和建模方法实现对非晶态金属合金及其复合材料的摩擦搅拌连接过程的基础科学理解。该研究项目将建立在有希望的初步实验基础上，以连接摩擦搅拌连接过程中相邻层中材料流动的理解，多尺度变形行为，分子动力学模拟和大规模有限元建模。拟议的工作将产生四方面的独特和基本的科学贡献。首先，本研究将增进对非晶金属及复合材料高应变加工过程中剪切混合及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产生的变形机制。第三部分涉及原子尺度模型，将创建响应高应变的自由体积演化的专有技术。最后，所提出的研究将有助于开发一个框架，以预测位置特定的属性，包括从温度，冷却速率和应变分布的空间分辨结构演变。所提出的研究的主要创新在于实现非晶态金属的均匀和堆叠结构，这是使用现有技术无法实现的，假设在非晶态金属成分之间的界面处的强烈剪切混合使表面氧化物破裂，从而导致原始金属流动和冶金结合。加工过程中的高应变预计将增加金属玻璃中原子级的不均匀性，从而使其恢复活力，并与铸造非晶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知识价值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.