2 research outputs found
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Laser Autogenous Brazing of Biocompatible, Dissimilar Metals in Tubular Geometries
The successful joining of dissimilar metal tubes would enable the selective use of the unique properties exhibited by biocompatible materials such as stainless steel and shape memory materials such as NiTi, to locally tailor the properties of implantable medical devices. The lack of robust joining processes for the dissimilar metal pairs found within these devices, however, is an obstacle to their development and manufacture. Traditional joining methods suffer from weak joints due to the formation of brittle intermetallics or use filler materials that are unsuitable for use within the human body. This study investigates a new process, Laser Autogenous Brazing, that utilizes a thermal accumulation mechanism to form joints between dissimilar metals without filler materials. This process has been shown to produce robust joints between wire specimens but requires additional considerations when applied to tubular parts. The strength, composition, and microstructure of the resultant joints between NiTi and Stainless Steel are investigated and the effects of laser parameters on the thermal profile and joining mechanism are studied through experiments and numerical simulations
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Effects of Interfacial Geometry on Laser Joining of Dissimilar NiTi to Stainless Steel Wires
Joining of the dissimilar metal pair NiTi to stainless steel is of great interest for implantable biomedical applications. Formation of brittle intermetallic phases requires that the joining processes limit the amount of over-melting and mixing along the interface. Thus, laser joining is a preferred method due to its ability to precisely control heat input. This study explores a method of using a cup and cone interfacial geometry, with no filler material, to increase the tensile strength of the joint. Not only does the cup and cone geometry increase the surface area of the interface, but it also introduces a shear component, which is shown to be beneficial to tensile strength of the wire as well. The fracture strength for various cone apex angles and laser powers is determined. Compositional profiles of the interfaces are analyzed. A numerical model is used for explanation of the processing