Abstract
Shape memory alloys (SMAs) have found widespread use in superelastic components and as compact, lightweight actuators. However, current use cases require SMAs to be joined to structural alloys (e.g., A17075, Inconel 718, 316L). At present, this is done mechanically (e.g., bolting or crimping) adding significant weight and volume, which reduces the benefit of using an SMA. Attempts at metallurgical bonds, which would not incur the weight/volume penalties of mechanical joints, have fallen short, often producing joints with deleterious phases and poor joint efficiencies (defined as σjoint/σmaterial). This is largely because the elemental composition and phase structure of SMAs are highly dissimilar to nearly all structural alloys. As a result, most of the possible composition gradients connecting the SMA to the structural alloy led to the formation of undesirable phases, typically brittle intermetallics. Thus, for a metallurgical joint to be successful, it must have a final composition gradient that results in favorable (strong, ductile) phases, while avoiding unfavorable (weak, brittle) ones. This joint requires two features: (1) a target final gradient that is known (or predicted) to be favorable; and (2) a technique for guiding the joining process to such a targeted final gradient. This work focuses on developing the former.
