Characterisation of Misfit Dislocations at Semicoherent Interfaces in Biphasic Functional Heusler Intermetallics

Eggeler, Yolita M.; Levin, E. S.; Wang, F.; Seshadri, R.; Pollock, T.; Gianola, DS

doi:10.1017/s1431927619010316

Cited by 1 publication

(1 citation statement)

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“…In the top grain, we can see the long axis of the ellipsoidal-shaped precipitates (similar precipitate shapes are reported by Kimuro et al [18]), highlighting their high aspect ratio. The long axis can extend to more than 10 μm and the short axis is in the range of 500 nm, shown in the magnified high angle annular dark field (HAADF) STEM images acquired after having oriented the sample in zone axis in Figure 1c and HH phases with different lattice parameters [26]. This is confirmed by the complementary selected area electron diffraction (SAED) pattern of zone axis [111] shown in Figure 1f.…”

Section: Precipitate Morphologymentioning

confidence: 62%

Interfacial structure and strain accommodation in two-phase NbCo1.2Sn Heusler intermetallics

Eggeler

Levin

Wang

et al. 2020

Phys. Rev. Materials

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Multiphasic intermetallic materials are attractive candidates for functional applications where the constituent phases alone do not meet the property targets. The interfaces at the phase boundaries in these materials are central to their macroscopic properties, with the details of the atomic structure underpinning local thermomechanical, electrical, and magnetic behavior. Here, we characterize the interface structure in the biphasic Nb-Co-Sn system consisting of NbCo2Sn full Heusler (FH) precipitates embedded in a NbCoSn half Heusler (HH) matrix, which exhibits semi-coherent interfaces with a 3.3% lattice parameter misfit that determines the constitution of the FH/HH interface on the nanometer scale. We use detailed transmission electron microscopy (TEM) and atomistic calculations to precisely determine the dislocation content and structure at the semi-coherent interface, which modulates the strain fields in a semiregular pattern. We find that the interface forms regularly spaced paired partial dislocations with a joint Burgers vector of a/2<110>, favored by misfit energy relief and chemical ordering. The interface exhibits numerous interface steps (disconnections) which in turn determine the precipitate morphology. Overall, the two phases show full coherency except in the vicinity of the misfit dislocation cores located every 11 nm, leading to a modulated strain field parallel to the interface, and no long-range strain fields as the interfacial dislocations accommodate the misfit strain.

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Section: Precipitate Morphologymentioning

confidence: 62%