GOALI: Dissimilar Metal Joining for Micro-Scale Medical Devices

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The research objective of this Grant Opportunity for Academic Liaison with Industry (GOALI) award is to investigate a novel joining process, autogenous (no filler material) laser brazing, for joining dissimilar biocompatible metals. Specifically, the project aims to develop a fundamental understanding of autogenous laser brazed joints by considering the thermal, kinetic, and thermodynamic aspects of the process, to experimentally and numerically investigate the effect of non-equilibrium processing conditions on the thermodynamic properties of the weld metal mixture and their effect on the resulting phases and interface microstructures, and to significantly enhance the knowledge of intermetallic phase formation in dissimilar material pairs and investigate potential avenues for their mitigation or elimination. The projected approach to address this issue is by limiting mixing of the materials and rapidly cooling the molten metal without the use of filler materials. Phase, microstructure, and strength will be characterized. The results will validate the modeling efforts which will consist of finite cooling rate phase formation and spatially resolved composition calculations.The benefits of this project are expected to enable the design and fabrication of innovative, implantable medical devices that selectively incorporate biocompatible metals with unique properties to significantly enhance device performance or introduce groundbreaking functionalities. The need to join these materials stems from the desire to integrate their unique properties in a robust and cost-effective manner. The main impediment to widespread use of dissimilar metal joints, however, is the formation of brittle intermetallic phases within the joints. The PI's strong support by a key industrial partner could lead to rapid development of real life applications of these devices with broad societal impact. The processing techniques, analysis methods, and predictive capabilities developed for the biocompatible metal pairs addressed in this project can be extended to other material pairs for aircraft structure and automobile battery applications.