Mechanical properties and fracture mechanisms of martensitic NiTi shape memory alloy based on various thermomechanical-processing microstructures

Yan, Bingyao; Zhang, Yanqiu; Jiang, Shengyao; Yu, Junbo; Sun, Dong; Tang, Ming

doi:10.1016/j.jallcom.2021.160797

Cited by 16 publications

(7 citation statements)

References 36 publications

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“…Clearly, tangled dislocation distributes unevenly in the matrix region of the 12.5%-deformed porous NiTi SMA sample, as well as the shear band. Both of them confirm the occurrence of severe inhomogeneous deformation [23]. As for the region o microcrack propagation, which is highlighted by the purple-dotted bordered rectangle in Figure 6, the inserted selected area electron diffraction patterns (SAEDPs) in Figure 7b depict the amorphous ring characteristics within the upper right area and the nanocrys talline grains with B2 (NiTi) and B19′ (NiTi) structures within the lower left area.…”

Section: Microstructure Characteristics Of Deformed Porous Niti Sma S...mentioning

confidence: 64%

“…Additionally, transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) are applied in the present study on an FEI Tecnai G 2 instrument to investigate the specific microstructure characteristics around microcrack regions. The TEM sample preparation method applied in the present study is similar to the reported one in the work of Yan et al [23] for bulk NiTi SMA; therefore, they would not be declared here.…”

Section: Microstructure Characteristics Of Fabricated Porous Niti Sma...mentioning

confidence: 76%

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Microstructure Characteristics of Porous NiTi Shape Memory Alloy Synthesized by Powder Metallurgy during Compressive Deformation at Room Temperature

Hu,

Shen,

Chen

et al. 2023

Metals

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Porous NiTi shape memory alloys (SMAs) possess compatible mechanical properties with human bones and can effectively reduce the risk of stress shielding and stress concentration; therefore, they have been termed promising candidates for orthopedic implants. However, microstructure characteristics of porous NiTi SMAs during plastic deformation have rarely been investigated. The present study aims to specifically investigate microstructure characteristics and the corresponding underlying mechanisms of fabricated porous NiTi SMAs via a conventional sintering (CS) process with NaCl space holder during compressive deformation at room temperature. To realize the aforementioned target, X-ray diffraction (XRD), scanning electron microscope (SEM), electron backscattered diffraction (EBSD), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM) are applied in the present study. The results show that the fabricated porous NiTi SMA is 51.8% for porosity, 181.65 μm for the average pore size, and 0.78 μm for the average grain size. Many Ni4Ti3 and NiTi2 phases are formed in the mixed matrix with dominant B2 (NiTi) and some B19′ (NiTi). Severe inhomogeneous deformation happens within compressed specimens, leading to the occurrence of tangled dislocation and shear bands. Microcracks occur within fabricated porous NiTi SMAs at a deformation degree of 9.2%; then, they extend quickly to form macrocracks, which finally results in the failure of regions between pores. The observed nanocrystallization and amorphization around microcrack tips within the 12.5%-deformed sample can be attributed to the relatively small grain size and the grain segmentation effect via statistically stored dislocation (SSD) and geometrically necessary dislocation (GND).

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Section: Microstructure Characteristics Of Deformed Porous Niti Sma S...mentioning

confidence: 64%

Section: Microstructure Characteristics Of Fabricated Porous Niti Sma...mentioning

confidence: 76%

Microstructure Characteristics of Porous NiTi Shape Memory Alloy Synthesized by Powder Metallurgy during Compressive Deformation at Room Temperature

Hu,

Shen,

Chen

et al. 2023

Metals

Self Cite

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“…The element sizes in the NiTi crystal zone of all the four models were set as 0.1 mm, while the ones at the edges and in the amorphous zones were refined to 0.03 mm. The material models for the NiTi crystal and the NiTi amorphous phase were obtained from the true stressstrain curves shown in figure 3, which was extracted from our previous study [21]. During the XFEM analysis, the lower boundaries of the models were fixed and a tensile load with the velocity of 0.1mm/s was imposed on the upper boundaries of the models.…”

Section: Modeling and Methodsmentioning

confidence: 99%

Influence of amorphous phase on crack initiation and propagation behaviours in NiTi shape memory alloy based on extended finite element simulation

Zhang

Guo

Jiang

2022

IOP Conf. Ser.: Mater. Sci. Eng.

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Local amorphous phases often appear in NiTi shape memory alloys (SMAs) which undergo a large degree of cold plastic deformation. Fracture damage is a common failure mode of NiTi SMAs in engineering application and it is usually caused by the crack initiation and propagation. The crack initiation and propagation behaviours in NiTi SMA parts containing amorphous phases have not been reported so far. In the present study, extended finite elements method (XFEM) was applied to investigate the influence of amorphous phase on crack initiation and propagation behaviours in a notched NiTi SMA specimen processed by cold plastic deformation. The results show that the amorphous zone has a significant influence on both the crack initiation and the crack propagation. Crack is easier induced if there exists amorphous phase in the NiTi SMA but it is difficult for the crack to pass through the amorphous zone.

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“…Shape memory alloy (SMAs) possess many good properties such as dimensional stability, shape memory properties, ductility and workability [1][2][3][4]. NiTi alloys are the most commercially viable SMAs and have been widely used in many practical applications.…”

Section: Introductionmentioning

confidence: 99%

Effects of Severe Plastic Deformation and Subsequent Annealing on Microstructures of a Ni50.6Ti49.4 Shape Memory Alloy

Zhang,

Wang,

et al. 2024

Metals

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High-pressure torsion (HPT) was applied to the Ni50.6Ti49.4 (at. %) alloy ingot up to 1/4, 2, 16, 32 and 48 turns under a pressure of 6.0 GPa. The samples were examined by X-ray diffraction (XRD), transmission electron microscope (TEM) and microhardness measurement. The results indicate that martensitic transformation and formation of amorphous phase occurred during the HPT process. As the HPT turns increased, the more the amorphous phase formed. The fraction of amorphization was analyzed based on the X-ray results. The microhardness increased with the HPT turns, which may be related to strain-induced martensite transformation, formation of the amorphous phase, increased dislocation densities and grain refinement. Differential scanning calorimetry (DSC) test revealed that shape memory alloys can be produced by HPT and post-HPT annealing from a NiTi ingot.

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Mechanical properties and fracture mechanisms of martensitic NiTi shape memory alloy based on various thermomechanical-processing microstructures

Cited by 16 publications

References 36 publications

Microstructure Characteristics of Porous NiTi Shape Memory Alloy Synthesized by Powder Metallurgy during Compressive Deformation at Room Temperature

Microstructure Characteristics of Porous NiTi Shape Memory Alloy Synthesized by Powder Metallurgy during Compressive Deformation at Room Temperature

Influence of amorphous phase on crack initiation and propagation behaviours in NiTi shape memory alloy based on extended finite element simulation

Effects of Severe Plastic Deformation and Subsequent Annealing on Microstructures of a Ni50.6Ti49.4 Shape Memory Alloy

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