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

Abstract

The mobility of twin boundaries in (at.%) Fe 70 Pd 30 , Fe 67 Pd 30 Co 3 and Fe 66.8 Pd 30.7 Mn 2.5 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 ( 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.

Influence of defects on the irreversible phase transition in the Fe-Pd doped with Co and Mn

“…The values obtained were Ha FePdCo = (1.0±0.1) eV and  oFePdCo =810 -(14±0.5) s, and Ha FePdMn = (1.0±0.1) eV and  oFePdMn =110 -(13±0.5) s. These values are in agreement with those previous obtained in these alloys, FePdCo and FePdMn, without the appearance of the BCT phase [24]. Moreover, the activation parameters are also in agreement with previous reported works in Fe 70 Pd 30 with and without the appearance of the BCT phase [24,25]. Consequently, the driving force controlling the development of P 1 is effectively the same as said before [25].…”

“…MT temperature peak. The measured enthalpies are 0.8 J/g and 0.7 J/g for FePdCo and FePdMn, respectively [14,23,24]. The Curie temperatures can be observed thorough the change in the baseline at T C =603 K for FePdCo and T C =540 K for FePdMn [13,24].…”

“…These amounts remain unless the alloy is annealed at high temperature and subsequently quenched [13]. After the first heating run up to 603 K, the P1 peak decreases its height markedly in both alloys, indicating that the density of quenched-in-defects was decreased [24].…”

“…During the second heating run up to the same temperature of the first, this peak decreases its height markedly in both alloys. In fact, this peak has been reported as P 1 [24][25][26]. The mechanism of the P 1 peak was related with a dislocation dragging mechanisms controlled by the migration of vacancies without break-away and is related to the intrinsic properties of the austenitic phase [25].…”

Study of the martensitic transition in Ni-Mn-Sn-Ti ferromagnetic shape memory alloys

“…In addition, in recent works, the influence of defects on the MT and the interaction between twin boundary and defects has been studied [13,14].…”