Size effects on the martensitic phase transformation of NiTi nanograins

Waitz, Thomas; Antretter, Thomas; Fischer, F.D.; Simha, N.K.; Karnthaler, H. P.

doi:10.1016/j.jmps.2006.06.006

Cited by 278 publications

(182 citation statements)

References 52 publications

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“…Nevertheless, the overall deformation of the laminate still contains a considerable amount of shear. Lamella widths of the BCVs decreases with the grain size [17] and BCVs down to a width as low as 0.9 nm have been observed via TEM, approximately corresponding to a stack of 4 atomic planes. Dislocations are only rarely observed; hence plastic deformation virtually plays no role [19].…”

Section: Compound Twinning In Polycrystalline Nanocrystalline Equiatimentioning

confidence: 91%

“…Then the IPS matrix P can be found from Eq.2 by substituting for F. The laminate plate averages the misfit of the individual BCVs to produce an overall invariant fit. The interfacial strains of the individual BCV are local strains with no long range consequences, so that they can be treated as a surface energy ߁ ௧௪ [17]. Also at this point the mathematical equivalence to the slipped formalism has been shown [15,18].…”

Section: Compound Twinning In Polycrystalline Nanocrystalline Equiatimentioning

confidence: 99%

See 1 more Smart Citation

Special cases of martensite compatibility: A near single-variant habit-plane and the martensite of nanocrystalline NiTi

Petersmann

Antretter

Waitz

2015

MATEC Web of Conferences

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Abstract. Lattice parameters measured near the high temperature (~1000°C) bcc α to hcp β transformation in an intermetallic Mo-containing γ-TiAl based alloy indicate a middle valued eigenvalue of the corresponding deformation gradient near 1. Habit-planes calculated under the assumption of a simple slip as lattice invariant shear, agree with experimentally determined orientations of the lens like plates recorded via electron backscattering. By contrast, twinning as invariant lattice shear has been investigated in nanocrystalline NiTi. Here the grain size causes the formation mechanism of the martensite to change from a "herring-bone" morphology faciliting a habit-plane between two twinned laminates and the austenite to a single laminate, which in the nonlinear theory formally cannot form a habit-plane with the austenite. Since this might cause high accommodation strains, the effectiveness of stress accommodation of martensite formed in neighboring grains of a polycrystal is investigated. Subsequent numerical microstructural modeling is outlined. The resulting energetically most favorable transformation sequence yields the transformation kinetics.

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Section: Compound Twinning In Polycrystalline Nanocrystalline Equiatimentioning

confidence: 91%

Section: Compound Twinning In Polycrystalline Nanocrystalline Equiatimentioning

confidence: 99%

Special cases of martensite compatibility: A near single-variant habit-plane and the martensite of nanocrystalline NiTi

Petersmann

Antretter

Waitz

2015

MATEC Web of Conferences

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“…The development of nanocrystalline Nitinol has been the subject of intensive research, because fine grained or nanocrystalline material shows a variety of different and improved properties compared to the conventional coarse-grained polycrystalline material [8][9][10][11][12][13][14][15][16]. Recently, bulk nanocrystalline NiTi has attracted much interest as a high-tech material, showing enhanced shape memory behavior and superelasticity with ultra high recovery stress [9,10].…”

Section: Introductionmentioning

confidence: 99%

“…Combining HPT and subsequent annealing treatments one can tune the grain size and as a result the properties of the material can be controlled [12][13][14]. One prominent example is the size effect that can significantly shift the transformation from the cubic B2 high temperature phase to the monoclinic B19' martensite; grains with a size less than 50 nm can even lead to the complete suppression of the transformation [15,16]. [17][18][19][20], melt spinning (MS) [21][22][23][24] and cold rolling [25,26].…”

Section: Introductionmentioning

confidence: 99%

Annealing behaviour of nanocrystalline NiTi (50 at% Ni) alloy produced by high-pressure torsion

Singh

Rösner

Prokofyev

et al. 2011

Philosophical Magazine

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International audienceAn equiatomic nanocrystalline NiTi alloy, deformed by high-pressure torsion (HPT) was investigated. The as-prepared bulk NiTi alloy consists of both amorphous and nanocrystalline phases. Crystallization and structural changes during annealing were investigated by differential scanning calorimetry (DSC), X-ray diffraction and transmission electron microscopy. The DSC thermograms and X-ray analyses reveal stress relaxation and partial crystallization below 500 K while grain growth of the nanocrystals occurs predominantly after heating to temperatures above 573 K. Along with the amorphous phase crystallization, a continuous growth of pre-existing nanocrystals that are retained after HPT is observed. The DSC signals observed during continuous heating experiments indicate an unusually large separation between the crystallization and the growth stages. A detailed analysis of the evolution of the enthalpy release upon annealing reveals reproducibly non-monotonous trends with annealing temperature that cannot be explained solely with nucleation and growth of crystalline volume fractions. Instead, the results can be rationalized by assuming a reverse amorphization process occuring during annealing at 523 K. This behavior, that also causes a large variation of the nanocrystals size after annealing at higher temperatures, is discussed with respect to the nanoscale microstructural heterogeneity after initial deformation processing

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“…[4,13,17], or by adding an energy penalty term associated with the higher gradients of the deformation, e.g. [5,12].…”

Section: Introductionmentioning

confidence: 99%

On dissipation, interfacial energy and size eﬀects in shape memory alloys

Stupkiewicz

Petryk

2009

ESOMAT 2009 - 8th European Symposium on Martensitic Transformations

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Abstract. This work presents a multiscale approach aimed at the modelling of evolution of martensitic microstructures with account for the interfacial energy effects. The total Helmholz free energy and the energy dissipated in the system are split into contributions from the bulk material, from phase interfaces and from other boundaries. Microstructure evolution is then determined by the incremental energy minimization. As an application, stress-induced transformation is considered which proceeds by formation and growth of internally twinned martensite plates within the austenite matrix. The interfacial energy is examined at three scales, namely at twin boundaries, austenite-martensite interfaces and at grain boundaries. Both atomic-scale and the elastic micro-strain interfacial energies are included and respective estimates are taken from the materials science literature or predicted using micromechanical finite element analysis. Examples are provided for the cubic-to-orthorhombic transformation in a CuAlNi shape memory alloy. They illustrate the effect of grain size on the macroscopic stress-strain response including the hysteresis width.

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Size effects on the martensitic phase transformation of NiTi nanograins

Cited by 278 publications

References 52 publications

Special cases of martensite compatibility: A near single-variant habit-plane and the martensite of nanocrystalline NiTi

Special cases of martensite compatibility: A near single-variant habit-plane and the martensite of nanocrystalline NiTi

Annealing behaviour of nanocrystalline NiTi (50 at% Ni) alloy produced by high-pressure torsion

On dissipation, interfacial energy and size eﬀects in shape memory alloys

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