Deformation induced martensite stabilization of NiTi in constrained composite systems

Bakhtiari, Sam; Li, Yingchao; Sarkar, Satyajit; Yang, Hong; Cui, Lishan; Liu, Yinong

doi:10.1016/j.msea.2022.144128

Cited by 7 publications

(2 citation statements)

References 35 publications

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“…The austenitic NiTi in the matrix transforms to stress-induced martensite (SIM) that is stable after unloading. This SIM is transformed back to austenite upon heating and the material and recovers residual strain due to the shape memory effect (SME) 31 . However, there is only partial recovery as the stress-induced transformation in the matrix is accompanied by the permanent plastic deformation of the Nb nano fibers.…”

Section: Discussionmentioning

confidence: 99%

Multifunctional metallic nanocomposite for overcoming the strength–ductility trade-off

Lanba,

Hamilton,

Melanson

et al. 2024

Sci Rep

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The actualization of high strength and ductility in alloys, in addition to providing strong, formable materials, can lead to reduced weights in practical applications. However, increasing strength typically comes at the cost of lowering the ductility and vice-versa, referred to as the strength–ductility trade-off. In this work, we investigate the thermo-mechanical response of a 3-element multifunctional NiTi–Nb nanocomposite material that overcomes this trade-off, as it exhibits a high strength of 980 MPa and an ultrahigh ductility of 58% at fracture. The remarkable properties are attributed to the underlying microstructure of Nb nanofibers dispersed in an NiTi matrix. Deformation is accommodated via the shape memory transformation of the active NiTi matrix in concert with elastoplastic deformation of Nb nanofibers embedded within the matrix. Consequently, the material exhibits multifunctionality and recovers deformation during heating via the reversion of the stress-induced martensitic transformation in the NiTi matrix. The high strength and high ductility of this 3-element nanocomposite material puts it amongst the best performing high-entropy alloys (HEAs) that are typically made up of five or more elements.

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Section: Discussionmentioning

confidence: 99%

Multifunctional metallic nanocomposite for overcoming the strength–ductility trade-off

Lanba,

Hamilton,

Melanson

et al. 2024

Sci Rep

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show abstract

“…Upon the subsequent cycling, homogeneous stress-induced transformation mode starts as soon as the loading is applied and the leftover B2 phase is transformed completely and fully reversible. is compressed once it appears, then instead in a tensile state (tensile d-spacing strain about 0.5%) after the first unloading, indicating that the residual martensite is subjected to an internal tensile stress along the loading direction [41,42]. This internal stress field is fully reversible in subsequent cycling.…”

Section: In-situ Micro-coupling Behavior By the Stress-induced Transf...mentioning

confidence: 99%

Endowing low fatigue for elastocaloric effect by refined hierarchical microcomposite in additive manufactured NiTiCuCo alloy

Feng,

Liu,

Yang

et al. 2024

Int. J. Extrem. Manuf.

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NiTiCu-based shape memory alloys have been considered as ideal materials for solid-state refrigeration due to their superb cycling stability for elastocaloric effect. However, the embrittlement and deterioration resulted from coarse grains and large-sized secondary phase restrict their application, and it is still challenging since the geometry is required. Here, bulk NiTiCuCo parts with excellent forming quality were fabricated by laser powder bed fusion (LPBF) technique. The as-fabricated alloy exhibits a refined three-phases hierarchical microcomposites structure formed based on the processing mode of LPBF, in which intricate dendritic Ti2Ni-NiTi composites and nano Ti2Cu uniformly embedded inside the NiTi-matrix. This configuration endows far superior elastocaloric stability compared to the cast counterpart. The low fatigue stems from the strong elastic coupling between the interphase with reversible martensite transformation inside the refined microcomposites, revealed by in-situ synchrotron high-energy X-ray diffraction. The fabrication of NiTiCuCo alloy via LPBF fill the bill of complex geometric structures for elastocaloric NiTiCu alloys. The interphase coupling micro-behaviors provide the guide for the design LPBF fabricated shape memory-based composites, enabling their applications with special demands on other functionalities.

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Variation of Poisson’s Ratio of NiTi During Pseudoelastic Deformation

Shariat,

Liu

2023

Shap. Mem. Superelasticity

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NiTi alloy exhibits a stress-induced B2 ↔ B19' martensitic transformation. This transformation is practically isochoric, thus has a Poisson’s ratio of 0.5. This imposes a complex interaction with elastic deformation which has a lower Poisson’s ratio and with plastic deformation which is not recoverable when interacting with other materials in a composite or an assembly, thus a challenge for the design of such materials or devices using them. This study investigated the variation of the Poisson’s ratio of a NiTi alloy during pseudoelastic deformation by means of the digital image correlation technique. The Poisson’s ratio of the alloy was found to increase from 0.39 in the apparent elastic deformation stage to 0.44 prior to the onset of the Lüders-type deformation and then to 0.48 after the passing of the Lüders band.

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Deformation induced martensite stabilization of NiTi in constrained composite systems

Cited by 7 publications

References 35 publications

Multifunctional metallic nanocomposite for overcoming the strength–ductility trade-off

Multifunctional metallic nanocomposite for overcoming the strength–ductility trade-off

Endowing low fatigue for elastocaloric effect by refined hierarchical microcomposite in additive manufactured NiTiCuCo alloy

Variation of Poisson’s Ratio of NiTi During Pseudoelastic Deformation

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