Effect of initial plastic strain on mechanical training of non-modulated Ni–Mn–Ga martensite structure

Szczerba, M.J.; Chulist, R.; Kopacz, S.

doi:10.1016/j.msea.2014.06.005

Cited by 14 publications

(3 citation statements)

References 24 publications

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“…However, the giant MFIS of 7%, 10% and 12% of longitudinal strain observed in 10M, 14M and NM martensites, respectively were all found in the initially trained microstructures of Ni-Mn-Ga single crystals. Training process is a sequence of uniaxial compression tests performed parallel to the {001} C direction referred to the cubic austenite phase [21]. The purpose of such a procedure: (i) is to lower the twinning stress in order to initiate strain by an external magnetic field and (ii) to refine the self-accommodated martensite structure achieving large MFIS determined by c/a ratio where c and a are the unit cell parameters of a particular martensite structure.…”

Section: Resultsmentioning

confidence: 99%

Non-Modulated Martensite Microstructure With Internal Nanotwins In Ni-Mn-Ga Alloys

Szczerba¹

2015

Archives of Metallurgy and Materials

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The self-accommodated non-modulated martensite of Ni-Mn-Ga single crystal was studied by transmission and scanning electron microscopy in the latter case using the electron backscatter diffraction technique. Three kinds of interfaces existing at different length scales were reported. The first, is the wavy and incoherent interface separating martensite variants observed on the micro-level with no-common crystallographic plane between them. The second is within a single martensite plate where the lattice rotates around one of the {110} pole to accommodate the interfacial curvature between martensite plates. Finally, at the nanoscale the third interface exists, a twin boundary separating internal nanotwins with the {112} type habit plane.Keywords: shape memory alloys; martensite; Ni-Mn-Ga single crystals; interface W pracy przeprowadzono obserwacje mikrostruktury monokryształu Ni-Mn-Ga charakteryzujący się nie-modulowaną strukturą martenzytyczną. Badania przeprowadzono z wykorzystaniem techniki transmisyjnej oraz skaningowej mikroskopii elektronowej. W przypadku drugiej metody zastosowano technikę elektronów wstecznie rozproszonych. Trzy rodzaje granic zostały zaobserwowane oraz opisane. Pierwsza granica jest niekoherentna i występuje w skali mikro pomiędzy płytkami martenzytu, które nie posiadają wspólnej płaszczyzny krystalograficznej o niskich indeksach Millera. Kolejna granica występuje wewnątrz pojedynczej płytki martenzytycznej, której towarzyszy rotacja sieci krystalicznej wokół kierunku {110} obszarów przedzielonych tą granicą w celu akomodacji wygięć granicy występującej między płytkami. W skali nanometrycznej można zaobserwować kolejną granicę równoległą do płaszczyzny krystalograficznej {112} (płaszczyzna bliźniacza), która rozdziela płytki nanobliźniaków.

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Section: Resultsmentioning

confidence: 99%

Non-Modulated Martensite Microstructure With Internal Nanotwins In Ni-Mn-Ga Alloys

Szczerba¹

2015

Archives of Metallurgy and Materials

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“…Mechanical training was performed on a parallelepiped specimen with 4.15 9 1.7 9 2.73 mm dimensions employing an Instron testing machine. It involved a sequence of uniaxial compression tests along\001[crystallographic directions, see for details [12,26]. Tests were conducted at room temperature under a compressive stress of up to 250 MPa and at a strain rate of 10 -3 s -1 .…”

Section: Methodsmentioning

confidence: 99%

“…Detailed understanding of the resulting martensite microstructure is paramount for the control of twin-boundary mobility and thus overall mechanical properties of the low-temperature martensite phase, which by analogy to conventional shape memory alloys requires pre-deformation by an external loading in order to realise the shape recovery accompanied by an output stress. The pre-deformation is mediated by the detwinning mechanism, operational during the training process often applied to harvest a single variant martensite state and conducted by a sequence of uniaxial compression tests along the \001[ directions referred to the austenite phase [12,13]. The initial self-accommodated microstructure as well as the detwinning process has been elucidated in more detail for magnetic Ni-Mn-Ga alloys, while considerably less attention has been called in this regard to Ni-Mn-(Sn, In, Sb) alloys [14][15][16][17][18][19][20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Self-accommodated and pre-strained martensitic microstructure in single-crystalline, metamagnetic Ni–Mn–Sn Heusler alloy

et al. 2017

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Metamagnetic shape memory alloys are a unique class of materials capable of large magnetic field-induced strain due to reverse martensitic phase transformation. A precondition for large shape change is martensite deformation, which heavily depends on microstructure. Elucidation of microstructure is therefore indispensable for strain control and deformation mechanics in such systems. The current paper reports on a self-accommodated martensitic microstructure in metamagnetic Ni 50 Mn 37.5 Sn 12.5 single crystal. The microstructure here is hierarchically organised at three distinct levels. On a large scale, martensite plate colonies, distinguished by intercolony boundaries, group individual martensitic plates. Plates are separated by interplate boundaries and deviate by 2.2°from an ideal twin relation. On the lower scale, plates are composed of subplate twins. Conjugation boundaries separating two pairs of twins arise in relation to a subplate microstructure. Modulation boundaries separating two variants with perpendicular modulation directions and with parallel c-axes also appear. Mechanical training frees larger plates from fine subplate microtwins bringing macro-lamellae into twin relation, what then permits further detwinning until a single variant state.

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Detwinning of a non-modulated Ni–Mn–Ga martensite: From self-accommodated microstructure to single crystal

Szczerba

Chulist

2015

Acta Materialia

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Effect of initial plastic strain on mechanical training of non-modulated Ni–Mn–Ga martensite structure

Cited by 14 publications

References 24 publications

Non-Modulated Martensite Microstructure With Internal Nanotwins In Ni-Mn-Ga Alloys

Non-Modulated Martensite Microstructure With Internal Nanotwins In Ni-Mn-Ga Alloys

Self-accommodated and pre-strained martensitic microstructure in single-crystalline, metamagnetic Ni–Mn–Sn Heusler alloy

Detwinning of a non-modulated Ni–Mn–Ga martensite: From self-accommodated microstructure to single crystal

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