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Joining of Nitinol

Among mechanical techniques, crimping or swaging are preferred.

Among adhesives, Cyanoacrylates, epoxies, etc. can be used. There are some biocompatible adhesives on the market that can also be sterilized.

In some cases the shape memory effect of the Nitinol alloy can be used as shrink-fit to connect two mating parts. For example a superelastic nitinol tube can be chilled, expanded while in martensite and then recovered onto its mating counterpart. A post-recovery interference or contact strain of about 1.5% is recommended for an effective joint. Designers must take into account tolerance stack-ups and installation clearance when designing a shape memory joint. Memry's alloy X (NiTiNb) is particularly useful for shape memory joints that require maintaining mechanical integrity at cryogenic temperatures.

Soldering is an effective means for joining nitinol to itself or dissimilar materials. The oxide layer must be removed for optimum solder wetting. Silver bearing solders can work effectively if combined with a very aggressive flux. Some companies use plating (Ni, Au, etc.) on nitinol to enhance solderability. Both solder and flux suffer from poor biocompatibility and will generally not be considered for use in medical implants.

TIG, laser, e-beam, resistance and plasma techniques can be used to weld nitinol to itself. Weld strength of about 70% of the raw material tensile strength can be achieved. Welding nitinol to stainless steel is much more difficult because of brittle intermetallics that form in the weld zone.