The influence of imposed strain on the development of microstructure and transformation characteristics of Ni–Ti shape memory alloys

Kocich, Radim; Kursa, Miroslav; Szurman, Ivo; Dlouhý, A.

doi:10.1016/j.jallcom.2010.12.003

Cited by 37 publications

(21 citation statements)

References 30 publications

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“…Anisotropic fragments are found to form a hierarchic system of low-angle and high-angle boundaries ( 3 and 60 , respectively). The planes of anisotropic fragments location are of the types {001}, {110} and {111}, which agrees with the data on the evolution of NiTi structure by severe plastic deformation to cause stabilization of the 2 phase [6]. Due to high gradients of defect density and lattice curvature-torsion, in some fragments dynamic recrystallization will occur ( Fig.…”

Section: Meso-and Microstructuresupporting

confidence: 87%

Structure of the near-surface layer of NiTi on the meso- and microscale levels after ion-beam surface treatment

Meisner¹,

Poletika

Meisner

et al. 2014

AIP Conference Proceedings

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Abstract. Using the EBSD, SEM and TEM methods, the structure of surface layer of polycrystalline NiTi alloy samples was examined after the modification of material surface by the pulsed action of mean-energy silicon ion beam. It was found that the ion beam treatment would cause grain fragmentation of the near-surface layer to a depth 5÷50 m; a higher extent of fragmentation was observed in grains whose close-packed planes were oriented approximately in the same direction as the ion beam was. The effect of high-intensity ion beam treatment on the anisotropic behavior of polycrystalline NiTi alloy and the mechanisms involved were also examined.

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Section: Meso-and Microstructuresupporting

confidence: 87%

Structure of the near-surface layer of NiTi on the meso- and microscale levels after ion-beam surface treatment

Meisner¹,

Poletika

Meisner

et al. 2014

AIP Conference Proceedings

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“…The uniaxial loading of a rectangular NiTi plate (a commercially rolled nitinol with the nominal composition of Ni-49.75at.%Ti) ( Kocich et al, 2011 ) is considered. The results are obtained for two-dimensional samples and by using 8-node biquadratic quadrilateral elements for all the simulations unless otherwise specified.…”

Section: Problem Formulation and Materials Propertiesmentioning

confidence: 99%

Microscale phase field modeling of the martensitic transformation during cyclic loading of NiTi single crystal

Esfahani

Ghamarian

Levitas

et al. 2018

International Journal of Solids and Structures

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A microscale phase field model developed in Levitas et al. (2004) and Idesman et al. (2005) is slightly advanced for different and anisotropic elastic moduli of phases and is employed for the study of the stressinduced cubic-monoclinic phase transition in NiTi single crystal involving all 12 martensitic variants. The model is scale-independent, without the gradient term, and it is applicable for any scale greater than 100 nm. This model includes strain softening and the corresponding transformation strain localization, and it reproduces a discrete martensitic microstructure. The model only tracks finite-width interfaces between austenite and the mixture of martensitic variants, and does not consider the interfaces between martensitic variants. The model is implemented as a UMAT subroutine in a commercial finite element (FE) package, ABAQUS. Multiple problems for a uniaxial cyclic loading are solved to study the effect of mesh, strain rate, crystal orientation, different numbers of pre-existing nuclei, and the magnitude of the athermal threshold on the stress-strain responses as well as the microstructure evolution. The obtained results exhibit that the microstructure and global stress-strain responses are practically independent of mesh discretization and the applied strain rate for relatively small strain rates. While the presence of the initial nuclei in the sample decreases the nucleation stress, it slightly increases the total energy dissipation. The observed microstructure, the sudden drop in the stress-strain curve after initiation of the martensitic transformation, and the absence of a similar jump for the reverse phase transformation are in qualitative agreement with known experiments. Changing the crystallographic orientation of the sample varies the entire behavior, namely, the variants which are involved in the phase transformation, the morphology of the associated microstructure, the stress-strain curve, and the total dissipation. Athermal threshold, in addition to the expected increase in the magnitude of hysteresis, leads to some strain hardening for the direct phase transformation. a b s t r a c t A microscale phase field model developed in Levitas et al. (2004) and Idesman et al. ( 2005) is slightly advanced for different and anisotropic elastic moduli of phases and is employed for the study of the stressinduced cubic-monoclinic phase transition in NiTi single crystal involving all 12 martensitic variants. The model is scale-independent, without the gradient term, and it is applicable for any scale greater than 100 nm. This model includes strain softening and the corresponding transformation strain localization, and it reproduces a discrete martensitic microstructure. The model only tracks finite-width interfaces between austenite and the mixture of martensitic variants, and does not consider the interfaces between martensitic variants. The model is implemented as a UMAT subroutine in a commercial finite element (FE) package, ABAQUS. Multiple problems for a uniaxial cyclic loading are solved to st...

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“…Its biocompatibility presupposes the alloy also for biomedical applications [24][25][26]. Therefore, HfNbTaTiZr can be considered as a modern biocompatible material, together with other innovative titanium-based alloys [27,28].…”

Section: Introductionmentioning

confidence: 99%

Microstructure and Mechanical Properties of Sintered and Heat-Treated HfNbTaTiZr High Entropy Alloy

Málek

Zýka

Lukáč

et al. 2019

Metals

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High entropy alloys (HEAs) have attracted researchers’ interest in recent years. The aim of this work was to prepare the HfNbTaTiZr high entropy alloy via the powder metallurgy process and characterize its properties. The powder metallurgy process is a prospective solution for the synthesis of various alloys and has several advantages over arc melting (e.g., no dendritic structure, near net-shape, etc.). Cold isostatic pressing of blended elemental powders and subsequent sintering at 1400 °C for various time periods up to 64 h was used. Certain residual porosity, as well as bcc2 (Nb- and Ta-rich) and hcp (Zr- and Hf-rich) phases, remained in the bcc microstructure after sintering. The bcc2 phase was completely eliminated during annealing (1200 °C/1h) and subsequent water quenching. The hardness values of the sintered specimens ranged from 300 to 400 HV10. The grain coarsening during sintering was significantly limited and the maximum average grain diameter after 64 h of sintering was approximately 60 μm. The compression strength at 800 °C was 370 MPa and decreased to 47 MPa at 1200 °C. Porosity can be removed during the hot deformation process, leading to an increase in hardness to ~450 HV10.

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The influence of imposed strain on the development of microstructure and transformation characteristics of Ni–Ti shape memory alloys

Cited by 37 publications

References 30 publications

Structure of the near-surface layer of NiTi on the meso- and microscale levels after ion-beam surface treatment

Structure of the near-surface layer of NiTi on the meso- and microscale levels after ion-beam surface treatment

Microscale phase field modeling of the martensitic transformation during cyclic loading of NiTi single crystal

Microstructure and Mechanical Properties of Sintered and Heat-Treated HfNbTaTiZr High Entropy Alloy

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