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Welding of High Temperature Shape Memory Alloys: a Feasibility Study

High Temperature Shape Memory Alloys (HTSMAs) Over the past decade research within the HTSMA industry has grown significantly.  As the markets for these alloys are increasing, more complex part geometries and dissimilar metal combinations are needed.  However, SMAs typically need to have a very specific stoichiometric composition, and as a result melting and casting operations are often limited. So in an effort to reduce costs and expand possible HTSMA applications, welding and joining of these materials are being explored. 

In this specific case NiTi-20Hf is being investigated, this alloy’s high hafnium concentration is beneficial as it can increase the transformation temperatures and promote precipitation strengthening.  However challenges arise during welding as one of its alloying elements, titanium, is very susceptible to oxidation.  To improve overall weld quality the project investigates solid state, and high-energy density processes in an effort to determine which method produces high quality joints with minimal oxidation, while also controlling the amount of precipitation that occurs during welding.

Industry Sponsor: NASA Glenn

Faculty: Antonio Ramirez, de Sousa Olivera

Graduate Student: Kaleb Ponder

Industry Contact: Othmane Benefane