THE TUNABLE MICROSTRUCTURE AND ITS INFLUENCE ON THE GIANT MAGNETOCALORIC EFFECT IN MAGNETIC SHAPE MEMORY ALLOYS Conference Paper uri icon

abstract

  • The entropy and adiabatic temperature changes upon martensitic transformation induced by external magnetic fields were studied in various NiCoMn-X (X=Sn, In) magnetic shape memory alloys (SMAs). Their relative cooling power were determined using an extensive thermodynamic framework. Tunable materials parameters that lead to an improved caloric effect were identified, including magnetic-field sensitivities of martensitic transformation temperatures, transition ranges, and thermal hysteresis, and magnetization changes across the transition. These properties were determined experimentally from simple magneto-thermo-mechanical measurements before and after various annealing treatments and were identified to be related to microstructural features such as atomic ordering and grain size. The results indicated that large grain size and disordered austenite phases yield small transition ranges and hysteresis for the studied compositions. The improved microstructure after annealing also reduced the required driving force used to induce the temperature change, thereby revealing the possibility of using magnetic SMAs in room temperature solid state refrigeration.

author list (cited authors)

  • Bruno, N. M., Karaman, I., Ross, J. H., Huang, Y. J., & Li, J. G.

citation count

  • 3

publication date

  • January 2015