CAREER: Surface Interactions in Dissimilar Material Joining

该学院早期职业发展奖(CAEREAR)支持两种不同金属热机械连接方法的基础研究，即磁脉冲焊接和搅拌摩擦盲铆接。随着制造商为轻型汽车、能源生产、消费设备或下一代医疗和电气产品寻找具有定制性能的创造性新结构或部件，不同金属的连接方法的需求越来越大。然而，不同的金属不能使用传统的熔化焊接方法连接。这项研究将为这两种连接工艺在不同金属中的广泛应用提供必要的理解。此外，该奖项还支持让学生参与研究的活动，提高学生对科学、技术和工程的兴趣，并向更广泛的人群推广先进制造业。研究目标是：(1)将连接界面上的局部力学性能(模数、硬度和韧性)与接头性能(拉伸强度和失效模式)关联起来；(2)验证磁脉冲焊接和搅拌摩擦盲铆接接头的抗拉强度随着金属间化合物或非晶层厚度增加到几十微米而增加，然后随着厚度的增加而降低的假设；(3)建立工艺参数、组织和接头性能之间的关系。为了实现第一个目标，将在不同的工艺条件下使用两种连接工艺制备连接样品。局部机械性能将通过微悬臂梁、微硬度和原位扫描电子显微镜测试来量化。接头性能将通过宏观准静态拉伸试验进行测量。为了达到第二个目标，可以通过调整工艺参数来制备不同厚度的金属间化合物或非晶层，并通过分析界面的扫描电子显微镜或透射电子显微镜图像来测量厚度。将建立层厚度和抗拉强度之间的关系。为了实现第三个目标，从扩散或金属间化合物生长的动力学模型中得到的一组控制方程将与有限元模拟相结合来预测局部相和微观成分体积分数，并结合不同工艺参数下的接触条件来预测接头性能。

This Faculty Early Career Development (CAREER) award supports fundamental research on two thermo-mechanical joining methods for dissimilar metals, namely magnetic pulse welding and friction stir blind riveting. Joining methods for dissimilar metals are in increasing demand as manufacturers are seeking creative new structures or components with tailored properties for lightweight vehicles, energy production, consumer devices, or next-generation medical and electrical products. However, dissimilar metals cannot be joined using traditional fusion-based welding methods. This research will provide much needed understanding to enable wide applications of these two joining processes for dissimilar metals. Additionally, this award supports activities to engage students in research; raise students' interest in science, technology, and engineering; and promote advanced manufacturing to a broader population. The research objectives are: (1) to correlate local mechanical properties (modulus, hardness, and toughness) across the joining interface with joint performance (tensile strength and failure modes); (2) to test the hypothesis that tensile strength of both magnetic pulse welding and friction stir blind riveting joints increases as the thickness of intermetallic compound or amorphous layer increases up to a few tens of micrometers, and then decreases as the thickness increases further; and (3) to establish the relationships between process parameters, microstructure, and joint performance properties. To achieve the first objective, joining samples will be prepared using the two joining processes under various process conditions. Local mechanical properties will be quantified through micro-cantilever, micro-hardness, and in situ scanning electron microscope testing. Joint performance will be measured through macro quasi-static tensile tests. To achieve the second objective, intermetallic compound or amorphous layers of different thickness values will be produced by adjusting process parameters, and the thickness will be measured by analyzing scanning electron microscope or transmission electron microscope images of the interfaces. A relationship between the layer thickness and tensile strength will be established. To achieve the third objective, a set of governing equations from kinetic modeling of diffusion or intermetallic compound growth will be coupled with finite element simulation to predict the local phase and microconstituent volume fractions, which together with the contact conditions under different process parameters will be used to predict the joint performance.