Low temperature a/b nanotwins in Ni50Mn25+xGa25−x Heusler alloys

Straka, Ladislav; Drahokoupil, Jan; Veřtát, Petr; Zelený, Michal; Kopeček, Jaromı́r; Sozinov, A.; Heczko, Oleg

doi:10.1038/s41598-018-30388-8

Cited by 16 publications

(15 citation statements)

References 49 publications

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“…This makes ( a/b ) MM ‐TBs, out of all theoretically possible TBs, [ 23 ] the most favorable to form an exact habit plane. [ 19 ] In agreement with this, they are also observed for 10M martensite with a very narrow spacing, [ 35 ] showing even some refinement. [ 36 ]…”

Section: The Quest: Identifying Twin Boundaries and Building Blocks Osupporting

confidence: 69%

“…[ 50 ] On level 2, the formation of ( a / b ) MM ‐TBs is an aspect which is still in the focus of current research. [ 35 ] Our investigation proposes that the amount of ( a / b ) MM ‐twinning can be controlled by the c T / a T ‐ratio, which will allow to examine the impact of these TBs systematically. At level 3 and 4, it is decisive for actuation to obtain type II instead of type I TBs as they exhibit a twinning stress lower by one order of magnitude.…”

Section: Preview: Microstructure Designmentioning

confidence: 99%

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Building Hierarchical Martensite

Schwabe

Niemann

Backen

et al. 2020

Adv Funct Materials

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Martensitic materials show a complex, hierarchical microstructure containing structural domains separated by various types of twin boundaries. Several concepts exist to describe this microstructure on each length scale, however, there is no comprehensive approach bridging the whole range from the nano‐ up to the macroscopic scale. Here, it is described for a Ni‐Mn‐based Heusler alloy how this hierarchical microstructure is built from scratch with just one key parameter: the tetragonal distortion of the basic building block at the atomic level. Based on this initial block, five successive levels of nested building blocks are introduced. At each level, a larger building block is formed by twinning the preceding one to minimize the relevant energy contributions locally. This naturally explains the coexistence of different types of twin boundaries. The scale‐bridging approach of nested building blocks is compared with experiments in real and reciprocal space. The approach of nested building blocks is versatile as it can be applied to the broad class of functional materials exhibiting diffusionless transformations.

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Section: The Quest: Identifying Twin Boundaries and Building Blocks Osupporting

confidence: 69%

Section: Preview: Microstructure Designmentioning

confidence: 99%

Building Hierarchical Martensite

Schwabe

Niemann

Backen

et al. 2020

Adv Funct Materials

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“…All abovementioned features of the YM behaviour point to a highly non-equilibrium state of the a/b twin structure over a broad temperature range. Probably, the a/b twin-related dramatic variations of the YM reflect recently reported reversible transitions to the nanotwin structure upon cooling of 10 M martensite [22].…”

Section: Role Of A/c and A/b Twins In The Internal Friction And Young's Modulus Temperature Spectrasupporting

confidence: 63%

“…As for the T-dot dependence, we mention first that a temperature-induced displacement of even relatively low-mobility Type I TB can be detected in the results presented by Straka et al [22]. In the optical images of Figure 5 [22], the position of the Type I TB changes with temperature.…”

Section: Origin Of T-dot and Time Dependence Of The Internal Frictionmentioning

confidence: 56%

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Transitory Ultrasonic Absorption in “Domain Engineered” Structures of 10 M Ni-Mn-Ga Martensite

Kustov

Saren

D’Agosto

et al. 2021

Metals

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In this work we create in 10 M Ni-Mn-Ga martensitic samples special martensitic variant structures consisting of only three twins separated by two a/c twin boundaries: Type I and Type II, with relatively low and very high mobility, respectively. The “domain engineered” structure thus created allows us to investigate the dynamics of a single highly mobile a/c twin boundary (TB). We show that temperature variations between 290 and 173 K in our samples induce an intense transitory internal friction at ultrasonic frequencies ca. 100 kHz, peaking around 215 K. A comparison is made of the data for the “domain engineered” sample with the behaviour of reference samples without a/c TB. Reference samples have two different orientations of a/b twins providing zero and maximum shear stresses in a/b twinning planes. We argue, first, that the transitory internal friction, registered at rather high ultrasonic frequencies, has magnetic origin. It is related with the rearrangement of magnetic domain structure due to the motion of a/c twin boundary induced by thermal stresses. This internal friction term can be coined “magnetic transitory internal friction”. Magnetic transitory internal friction is a new category, linking the classes of transitory and magnetomechanical internal friction. Second, the structure of a/b twins is strongly non-equilibrium over a broad temperature range. As a consequence, the Young’s modulus values of the samples with maximum shear stress in a/b twinning planes can take any value between ca. 15 and 35 GPa, depending on the prehistory of the sample.

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Adaptive Phase or Variant Formation at the Austenite/Twinned Martensite Interface in Modulated Ni–Mn–Ga Martensite

Chulist,

Wójcik,

Sozinov

et al. 2024

Adv Funct Materials

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The crystal structure and transformation path from austenite to 10M martensite in Ni–Mn–Ga single crystal are examined employing high‐energy synchrotron radiation, scanning, and transmission electron microscopy. Using temperature gradient, an austenite/twinned martensite interface is stabilized revealing the crystal structure and microstructure of both phases and the transformation sequence across the interface. Depending on the distance from the interface, three distinct types of martensite crystal lattice, namely simple tetragonal and two monoclinic modulated ones, that is, 10M′ and 10M are confirmed. In situ measurements show that lattice mismatch formed at the habit plane is compensated by the formation of micro‐twinned and branched martensite along with an elastic change in lattice parameters. It is shown that the characteristics for periodic shuffling twin boundaries, such as modulation twins or inverted stacking faults, are installed in later stages of transformation. In other words, large microstructure elements that most efficiently accommodate the strain are installed first, and then smaller elements are operable. Overall, the experimental results show that the crystal lattice does not adapt modulated phase at the habit plane and cannot be built up from simple non‐modulated tetragonal blocks but rather a specific sequence of phase transformations using shear/shuffling deformation takes place.

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Low temperature a/b nanotwins in Ni50Mn25+xGa25−x Heusler alloys

Cited by 16 publications

References 49 publications

Building Hierarchical Martensite

Building Hierarchical Martensite

Transitory Ultrasonic Absorption in “Domain Engineered” Structures of 10 M Ni-Mn-Ga Martensite

Adaptive Phase or Variant Formation at the Austenite/Twinned Martensite Interface in Modulated Ni–Mn–Ga Martensite

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