Deformation Behavior, Structure and Properties of an Equiatomic Ti–Ni Shape Memory Alloy Compressed in a Wide Temperature Range

Komarov, Victor; Khmelevskaya, I. Yu.; Karelin, R. D.; Postnikov, Ivan; Korpała, Grzegorz; Kawalla, Rudolf; Prahl, Ulrich; Yusupov, V. S.; Прокошкин, С. Д.

doi:10.1007/s12666-021-02355-x

Cited by 13 publications

(12 citation statements)

References 24 publications

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“…The deformation value was determined based on the following relationship: Ɛ = d/(D + d), where d is the diameter of the sample, and D is the diameter of the mandrel. The shape recovery rate (SRR) was determined as a ratio of recovered strain to induced strain, Ɛ rt /Ɛ i *100% [ 35 ]. After the strain induction, the sample was heated in oil to implement the shape memory effect and determine the Ɛ rt and TRSR.…”

Section: Methodsmentioning

confidence: 99%

Production, Mechanical and Functional Properties of Long-Length TiNiHf Rods with High-Temperature Shape Memory Effect

et al. 2023

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In the present work, the possibility of manufacturing long-length TiNiHf rods with a lowered Hf content and a high-temperature shape memory effect in the range of 120–160 °C was studied. Initial ingots with 1.5, 3.0 and 5.0 at.% Hf were obtained by electron beam melting in a copper water-cooled stream-type mold. The obtained ingots were rotary forged at the temperature of 950 °C, with the relative strain from 5 to 10% per one pass. The obtained results revealed that the ingots with 3.0 and 5.0 at.% Hf demonstrated insufficient technological plasticity, presumably because of the excess precipitation of (Ti,Hf)2Ni-type particles. The premature destruction of ingots during the deformation process does not allow obtaining high-quality long-length rods. A long-length rod with a diameter of 3.5 mm and a length of 870 mm was produced by rotary forging from the ingot with 1.5 at.% Hf. The obtained TiNiHf rod had relatively high values of mechanical properties (a dislocation yield stress σy of 800 MPa, ultimate tensile strength σB of 1000 MPa, and elongation to fracture δ of 24%), functional properties (a completely recoverable strain of 5%), and a required finishing temperature of shape recovery of 125 °C in the as-forged state and of 155 °C after post-deformation annealing at 550 °C for 2 h.

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Section: Methodsmentioning

confidence: 99%

Production, Mechanical and Functional Properties of Long-Length TiNiHf Rods with High-Temperature Shape Memory Effect

et al. 2023

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“…The size of the sample was 0.5 × 0.5 × 10 mm 3 . The method consists of the following sequence of operations: consecutively increasing the induced strain; determining the value of the residual strain after unloading and the difference between the induced strain and residual strain (elasticity and superelasticity effect); heating it to above the A s temperature for the strain recovery; indicating the values of residual strain and recovered strain (shape memory effect) [ 9 ]. The total recoverable strain

is defined when the residual strain is 0%, and consequently, the shape recovery rate is 100%.…”

Section: Methodsmentioning

confidence: 99%

“…Conventional manufacturing technologies of NiTi SMA usually include hot deformation by rolling or forging at recrystallization temperatures and above. Elevated deformation temperatures lead to the formation of the recrystallized structure with a size of about 25–30 microns and a relatively low values of the completely recoverable strain of 4% and lower [ 8 , 9 ].…”

Section: Introductionmentioning

confidence: 99%

Evolution of Structure and Properties of Nickel-Enriched NiTi Shape Memory Alloy Subjected to Bi-Axial Deformation

et al. 2023

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The effect of a promising method of performing a thermomechanical treatment which provides the nanocrystalline structure formation in bulk NiTi shape memory alloy samples and a corresponding improvement to their properties was studied in the present work. The bi-axial severe plastic deformation of Ti-50.7at.%Ni alloy was carried out on the MaxStrain module of the Gleeble system at 350 and 330 °C with accumulated true strains of e = 6.6–9.5. The obtained structure and its mechanical and functional properties and martensitic transformations were studied using DSC, X-ray diffractometry, and TEM. A nanocrystalline structure with a grain/subgrain size of below 80 nm was formed in bulk nickel-enriched NiTi alloy after the MaxStrain deformation at 330 °C with e = 9.5. The application of MaxStrain leads to the formation of a nanocrystalline structure that is characterized by the appearance of a nano-sized grains and subgrains with equiaxed and elongated shapes and a high free dislocation density. After the MaxStrain deformation at 330 °C with e = 9.5 was performed, the completely nanocrystalline structure with the grain/subgrain size of below 80 nm was formed in bulk nickel-enriched NiTi alloy for the first time. The resulting structure provides a total recoverable strain of 12%, which exceeds the highest values that have been reported for bulk nickel-enriched NiTi samples.

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“…In other words, the sample deforms during cooling and recovers during heating; these characteristics are due to the phase change called thermoelastic martensitic transformation. In addition, it is important to mention that the combined mechanical properties obtained in SMAs depend on the chemical composition and the structure formed during thermomechanical processing [ 7 , 8 , 9 ]. Several alloys with shape memory and superelasticity are reported in the literature, but only a few have been commercially developed, such as NiTi, NiTiX (where X is a ternary element), and CuZnAl [ 10 , 11 ].…”

Section: Introductionmentioning

confidence: 99%

Thermomechanical Characterization and Modeling of NiTi Shape Memory Alloy Coil Spring

et al. 2023

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Today, shape memory alloys (SMAs) have important applications in several fields of science and engineering. This work reports the thermomechanical behavior of NiTi SMA coil springs. The thermomechanical characterization is approached starting from mechanical loading–unloading tests under different electric current intensities, from 0 to 2.5 A. In addition, the material is studied using dynamic mechanical analysis (DMA), which is used to evaluate the complex elastic modulus E* = E′ − iE″, obtaining a viscoelastic response under isochronal conditions. This work further evaluates the damping capacity of NiTi SMA using tan δ, showing a maximum around 70 °C. These results are interpreted under the framework of fractional calculus, using the Fractional Zener Model (FZM). The fractional orders, between 0 and 1, reflect the atomic mobility of the NiTi SMA in the martensite (low-temperature) and austenite (high-temperature) phases. The present work compares the results obtained from using the FZM with a proposed phenomenological model, which requires few parameters for the description of the temperature-dependent storage modulus E′.

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Deformation Behavior, Structure and Properties of an Equiatomic Ti–Ni Shape Memory Alloy Compressed in a Wide Temperature Range

Cited by 13 publications

References 24 publications

Production, Mechanical and Functional Properties of Long-Length TiNiHf Rods with High-Temperature Shape Memory Effect

Production, Mechanical and Functional Properties of Long-Length TiNiHf Rods with High-Temperature Shape Memory Effect

Evolution of Structure and Properties of Nickel-Enriched NiTi Shape Memory Alloy Subjected to Bi-Axial Deformation

Thermomechanical Characterization and Modeling of NiTi Shape Memory Alloy Coil Spring

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