Magnetostrictive Terfenol-D alloys printed via material extrusion

Magnetostrictive terbium–iron–dysprosium alloys, commonly known as Terfenol-D, deform in response to magnetic fields and exhibit changes in magnetization under mechanical stress. This unique, instantaneous magneto-mechanical coupling enables the generation and detection of various acoustic waveforms, including surface, shear, and longitudinal waves. However, the widespread adoption of Terfenol-D in acoustic transducer applications is limited by its manufacturing challenges. Terfenol-D is brittle, making conventional subtractive machining techniques, such as turning or milling, difficult. Integrating Terfenol-D transducers into host structures currently relies on mechanical clamping, welding, or adhesive bonding, all of which are labor-intensive and often unreliable in radioactive or high-temperature environments. To address these challenges, this study presents a comprehensive additive manufacturing strategy for Terfenol-D. A novel colloidal ink composed of Terfenol-D nanoparticles, predominantly around 155 nm in effective diameter, was synthesized via high-energy ball milling and subsequently printed onto stainless steel substrates using a commercial material extrusion (MEX) system. The printed structures were sintered using either conventional thermal treatment or electric field-assisted sintering. While thermal sintering promoted particle coalescence, the severe thermal expansion mismatch at the interface weakened adhesion and led to delamination, whereas electric field-assisted sintering achieved strong diffusion bonding. Scanning electron microscopy revealed that the MEX process produced highly dense Terfenol-D thin films on stainless steel substrates, and X-ray diffraction confirmed the preservation of the alloy composition, indicating minimal oxidation or contamination. These findings confirm that material extrusion is a promising route to streamline the fabrication and integration of magnetostrictive devices.