Smart materials find a wide range of application areas due to their varied response to external stimuli. The different areas of application can be in our day to day life, aerospace, civil engineering applications, and mechatronics to name a few. Magnetostrictive materials are a class of smart materials that can convert energy between the magnetic and elastic states. Galfenol is a magnetostrictive alloy comprised primarily of the elements iron (Fe) and gallium (Ga). Galfenol exhibits a unique combination of mechanical and magnetostrictive (magnetic) properties that legacy smart materials do not. Galfenol’s ability to function while in tension, mechanical robustness and high Curie temperature (600 °C) is attracting interest for the alloy’s use in mechanically harsh and elevated temperature environments. Applications actively being investigated include transducers for down-hole use, next generation fuel injectors, sensing and energy harvesting devices.
Understanding correlations between microstructure, electronic structure and functional response is key to developing novel magnetostrictive materials for sensor and actuator technologies.
To this end, in the first part of this thesis we report successful fabrication and investigation on magnetic and magnetostrictive properties of mechanically alloyed Fe81Ga19 compounds. For the first time we could measure magnetostrictive properties of mechanically alloyed FeGa compounds. A maximum saturation magnetostriction of 41 ppm was achieved which is comparable to those measured from polycrystalline FeGa alloys prepared by other processing techniques, namely gas atomization and cold rolling. Overall, this study demonstrates the feasibility of large-scale production of FeGa polycrystalline alloys powders by a simple and cost-effective mechanical alloying technique.
In the second part of this work, we report for the first time, experimental results pertaining to successful fabrication and advanced characterization of a series of Er/Gd-doped -textured polycrystalline alloys of nominal composition, Fe83Ga17Erx (0The goal of this project is 1) Developing new synthesis techniques including mechanical alloying for fabricating FeGa alloys and 2) To develop rare earth doped FeGa alloys with focus in Er and Gd as rare-earth which have a much lower price compared with the heavy rare earth magnetostrictive materials and are easier to use in harsh mechanical environments.
- Prof. Vincent G. Harris (Advisor)
- Prof. Yongmin Liu
- Dr. Yajie Chen