Training, Microstructure, and Magneto-Mechanical Properties of Ni-Mn-Ga Magnetic Shape-Memory Alloys

The microstructures and magneto-mechanical strain experiments of differently trained Ni-Mn-Ga single crystal and foam samples are shown in this thesis. Magneto-mechanical tests were performed over high numbers of magneto-mechanical cycles. The strain performance is analyzed and compared with prior results. The strain behavior is then analyzed in combination with surface characterization and qualitative tendencies are given as possible explanations for the examined behavior. It can be shown that inefficiently trained samples have the tendency to have lower initial strains but therefore can sustain 100 million magnetic-field-induced cycles. Effectively trained sample tend to have higher initial strain but also seem to fail after fewer cycles. It is also shown that the magneto-mechanical properties tend to be mostly influenced by the presence of space holder granulates left after etching