Mobility of Twin Boundaries in Fe-Pd-Based Ferromagnetic Shape Memory Alloys

The mobility of twin boundaries in (at.%) Fe70Pd30, Fe67Pd30Co3 and Fe66.8Pd30.7Mn2.5 has been studied by mechanical spectroscopy. Measurements were carried out in amplitude dependent damping regime. A new model based on the Friedel theory was developed to obtain the activation energy (similar to 2 kJ/mol) for twin boundaries motion. The model describes the amplitude dependent damping from thermally assisted break-away of dislocations. Interaction processes among twin boundaries, dislocations and vacancies during the recovery of the structure are also discussed. Moreover, a damping peak related to a dislocation dragging mechanism controlled by vacancies migration without break-away, earlier reported in Fe-Pd alloys, was also found in Fe-Pd-Co and Fe-Pd-Mn alloys.