Welding of Shape Memory Alloy & Stainless Steel Torque Tube

To demonstrate a unique application for shape memory alloys, a torque tube design was formulated.  This involved electrical-discharge machining of a tube approximately 3/8” OD from a plate of nitinol.   A butt joint was designed to allow for welding of the nitinol to a similar-sized stainless steel tube, using a consumable filler insert.  Orbital GTAW was used to produce the welds.  This paper describes the joint preparation and welding process, as well as metallurgical analyses of the welds.  Mechanical test results will be discussed, and the design and construction of a demonstration fixture will be shown.