Quantitative Studies of microstructural phase transformation in Nickel–Titanium

Kimiecik, Michael; Jones, J. W.; Daly, Samantha

doi:10.1016/j.matlet.2012.12.063

Cited by 26 publications

(21 citation statements)

References 16 publications

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“…e.g. [19,88,55,38], and references therein). We shall call attention to specific experimental observations and make comparisons to our own results in the chapters that follow.…”

Section: Literature Reviewmentioning

confidence: 99%

Interplay of martensitic phase transformation and plastic slip in polycrystals

2013

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we propose a modelling framework to explore the interplay between martensitic phase transformations and plastic slip in polycrystalline materials, with an eye towards computational efficiency. The resulting framework uses a convexified potential for the internal energy density to capture the stored energy associated with transformation at the meso-scale, and introduces kinetic potentials to govern the evolution of transformation and plastic slip.The framework is novel in the way it treats plasticity on par with transformation.We implement the framework in the setting of anti-plane shear, using a staggered implicit/explict update: we first use a Fast-Fourier Transform (FFT) solver based on an Augmented Lagrangian formulation to implicitly solve for the full-field displacements of a simulated polycrystal, then explicitly update the volume fraction of martensite and plastic slip using their respective stick-slip type kinetic laws. We observe that, even in this simple setting with an idealized material comprising four martensitic variants and four slip systems, the model recovers a rich variety of SMA type behaviors. We use this model to gain insight into the isothermal behavior of stress-stabilized martensite, looking at the viii effects of the relative plastic yield strength, the memory of deformation history under non-proportional loading, and several others.We extend the framework to the generalized 3-D setting, for which the convexified potential is a lower bound on the actual internal energy, and show that the fully implicit discrete time formulation of the framework is governed by a variational principle for mechanical equilibrium. We further propose an extension of the method to finite deformations via an exponential mapping. We implement the generalized framework using an existing Optimal Transport Mesh-free (OTM) solver. We then model the α-γ and α-ε transformations in pure iron, with an initial attempt in the latter to account for twinning in the parent phase. We demonstrate the scalability of the framework to large scale computing by simulating Taylor impact experiments, observing nearly linear (ideal) speed-up through 256 MPI tasks. Finally, we present preliminary results of a simulated Split-Hopkinson Pressure Bar (SHPB) experiment using the α-ε model. ix

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“…e.g. [19,88,55,38], and references therein). We shall call attention to specific experimental observations and make comparisons to our own results in the chapters that follow.…”

Section: Literature Reviewmentioning

confidence: 99%

Interplay of martensitic phase transformation and plastic slip in polycrystals

2013

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“…First, the length scales of microstructure interfaces in an SMA routinely span 10 nm to 1 mm, making it difficult to use a single measurement technique to simultaneously observe all of the critical features during micro-structure evolution (Li, 2002;Zhang et al, 2000;Liu et al, 1999Liu et al, , 2000Inamura et al, 2012;Nishida et al, 1988Nishida et al, , 2012Coughlin et al, 2012;Norfleet et al, 2009). Second, most experimental techniques for observing microstructure evolution across the relevant length scales are limited to surface observations (Gall et al, 2002;Kimiecik et al, 2013Kimiecik et al, , 2016Laplanche et al, 2017;Kim et al, 2015;Shaw, 2000;Paul et al, 2017) and typically cannot measure the out-of-plane deformations that result from these three-dimensional deformation mechanisms. Third, the three-dimensional measurement techniques that do exist are either destructive and prohibit in situ measurements (Hornbuckle et al, 2015;Henrie et al, 2005;Liu et al, 2015) or are averaged over millions to billions of grains (Stebner et al, 2013;Dunand et al, 1996;Khalil-Allafi et al, 2004;Buhrer et al, 1983).…”

Section: Introductionmentioning

confidence: 99%

Measuring stress-induced martensite microstructures using far-field high-energy diffraction microscopy

Bucsek¹,

Dale²,

Ko³

et al. 2018

Acta Cryst Sect A

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Modern X-ray diffraction techniques are now allowing researchers to collect long-desired experimental verification data sets that are in situ, three-dimensional, on the same length scales as critical microstructures, and using bulk samples. These techniques need to be adapted for advanced material systems that undergo combinations of phase transformation, twinning and plasticity. One particular challenge addressed in this article is direct analysis of martensite phases in far-field high-energy diffraction microscopy experiments. Specifically, an algorithmic forward model approach is presented to analyze phase transformation and twinning data sets of shape memory alloys. In the present implementation of the algorithm, the crystallographic theory of martensite (CTM) is used to predict possible martensite microstructures (i.e. martensite orientations, twin mode, habit plane, twin plane and twin phase fractions) that could form from the parent austenite structure. This approach is successfully demonstrated on three single- and near-single-crystal NiTi samples where the fundamental assumptions of the CTM are not upheld. That is, the samples have elastically strained lattices, inclusions, precipitates, subgrains, R-phase transformation and/or are not an infinite plate. The results indicate that the CTM still provides structural solutions that match the experiments. However, the widely accepted maximum work criterion for predicting which solution of the CTM should be preferred by the material does not work in these cases. Hence, a more accurate model that can simulate these additional structural complexities can be used within the algorithm in the future to improve its performance for non-ideal materials.

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“…The advent of non-destructive in situ experiments is providing data that elucidate physics at the length scales of micromechanical theories. In situ microscopy techniques, together with digital image correlation, provide a means for visually studying the bridges between microscopic scales and macroscopic responses and are unequivocally well suited for observing films, strips, sheets, and other geometries where surface effects dominate the structural response of components [9][10][11][12]. In situ neutron diffraction, on the other hand, provides a means to simultaneously probe the conglomerate responses of millions to billions of crystals in bulk samples of several millimeters to centimeters in size, concurrent with macroscopic behaviors [13][14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

In Situ Neutron Diffraction Studies of Large Monotonic Deformations of Superelastic Nitinol

Stebner

Paranjape

Clausen

et al. 2015

Shap. Mem. Superelasticity

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Superelastic Nitinol micromechanics are studied well into plastic deformation regimes using neutron diffraction. Insights are made into the nature of initial transformation, bulk transformation, plastic deformation, and unloading. Schmid factor predictions based on habit plane variants are found to best describe the very first grains that transform, prior to the transformation plateaus. However, the bulk transformation behavior that gives rise to transformation plateaus violates single crystal Schmid factor analyses, indicating that in bulk polycrystals, it is the effect of grain neighborhoods, not the orientations of individual grains, that drives transformation behaviors. Beyond the plateaus, a sudden shift in micromechanical deformation mechanisms is observed at *8.50 %/4.75 % tension/compression engineering strain. This mechanism results in reverse-phase transformation in both cases, indicating a strong relaxation in internal stresses of the samples. It is inferred that this mechanism is most likely initial bulk plastic flow, and postulated that it is the reason for a transition from fatigue life enhancement to detriment when pre-straining superelastic Nitinol. The data presented in this work provide critical datasets for development and verification of both phenomenological internal variable-driven and micromechanical theories of transformationplasticity coupling in shape memory alloys.

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Quantitative Studies of microstructural phase transformation in Nickel–Titanium

Cited by 26 publications

References 16 publications

Interplay of martensitic phase transformation and plastic slip in polycrystals

Interplay of martensitic phase transformation and plastic slip in polycrystals

Measuring stress-induced martensite microstructures using far-field high-energy diffraction microscopy

In Situ Neutron Diffraction Studies of Large Monotonic Deformations of Superelastic Nitinol

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