A collaboration between Texas A&M University and Shanghai Jiao Tong University, China, investigates the microstructural design of magnetic shape memory alloys (MSMAs) tailored for highly efficient energy conversion. The thermoelastic coupling inherent in these materials provides a route to considerable energy-saving devices based on harvesting of otherwise wasted mechanical work. With the addition of magnetic and electronic couplings, MSMAs as multicaloric materials offer many possibilities for conversion into useful forms of energy. It has also recently been shown that the thermo-elastic process can be harnessed for refrigeration, with large theoretical efficiency gain as compared to current technology. The researchers implement a comprehensive program to study the magneto-thermo-mechanical coupling in MSMAs. The US team collaborates with the Chinese group to fabricate materials with a wide range of controlled microstructures and orientations (single crystals, bi-crystals, controlled texture) and characterize the magneto-thermo-mechanical behavior as a function of processing parameters and microstructural features related to grain size, particle size, volume fraction, morphology, and texture. This is paired with a detailed characterization of the magnetic structure and its coupling to the microstructure. The overall goal is to overcome current material shortcomings, e.g., reduce the transformation hysteresis, increase the toughness, and improve the actuation stress. An important practical target is to achieve inexpensive MSMAs based on controlled solidification and microstructure design, thus providing a highly efficient platform for energy conversion applications.
The research not only advances the fundamental understanding of the multi-functional alloys, but highly efficient MSMAs can potentially revolutionize the field of solid-state cooling. Education benefits include the participation of US students in the international research activities at Shanghai Jiao Tong University, one of the leading materials research universities in China, as well as the establishment of a joint degree program between Texas A&M and Shanghai Jiao Tong universities. The work of the Chinese investigators is supported by the National Natural Science Foundation of China.