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13 pages, 7283 KiB

Open AccessArticle

Microstructure and Mechanical Behavior of Cu-Al-Ni-B Alloys with Thermoelastic Martensitic Transformation

by Alexey E. Svirid, Sergey V. Afanasiev, Denis I. Davydov, Natalia N. Kuranova, Vladimir V. Makarov, Vladimir G. Pushin and Yurii M. Ustyugov

Metals 2023, 13(5), 967; https://doi.org/10.3390/met13050967 - 17 May 2023

Cited by 1 | Viewed by 1020

Abstract

For the first time, using optical, scanning, and transmission electron microscopy and X-ray phase analysis in combination with measurements of tensile mechanical properties, we obtained data on the structural features of the polycrystalline shape-memory eutectoid Cu-Al-Ni-(B) alloys doped by aluminum (of 10 and [...] Read more.

For the first time, using optical, scanning, and transmission electron microscopy and X-ray phase analysis in combination with measurements of tensile mechanical properties, we obtained data on the structural features of the polycrystalline shape-memory eutectoid Cu-Al-Ni-(B) alloys doped by aluminum (of 10 and 14 wt% Al in total amount), nickel (of 3, 4, and 4.5 wt% Ni), and boron (0.02–0.3 wt% B) in various compositions. The effect of boron on the grain sizes, structure, phase composition, and mechanical properties of shape memory (SM) alloys has been studied. The localization of aluminum borides in the structure was investigated and an effect of grain growth inhibition in the (α + β) and β Cu-Al-Ni-B alloys was established, both in the cast state of the alloys considered and after their heat treatment. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Behaviour of Shape Memory Alloys)

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14 pages, 389 KiB

Open AccessArticle

Role of Magnetism in Lattice Instability and Martensitic Transformation of Heusler Alloys

by Ilya Razumov and Yuri Gornostyrev

Metals 2023, 13(5), 843; https://doi.org/10.3390/met13050843 - 25 Apr 2023

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Abstract

Heusler alloys are subject of considerable interest because they exhibit a martensitic transformation (MT), a shape-memory effect and a giant magnetocaloric effect. As it is commonly believed, the pronounced magnetoelastic coupling plays a crucial role; however, the effect of alloy composition on MT [...] Read more.

Heusler alloys are subject of considerable interest because they exhibit a martensitic transformation (MT), a shape-memory effect and a giant magnetocaloric effect. As it is commonly believed, the pronounced magnetoelastic coupling plays a crucial role; however, the effect of alloy composition on MT is still under discussion. To describe the features of MT in Ni

_{0.75 - x}

Mn

_{x}

Ga

_{0.25}

Heusler alloys, the phenomenological model that consistently considers the magnetic and lattice degrees of freedom and their mutual interplay has been developed. The magnetic entropy contribution was estimated within the framework of the microscopic approach. The proposed model allows us to describe the dependence of the martensitic transformation start temperature

M_{s} (x)

on the Mn concentration x in reasonable agreement with the experiment. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Behaviour of Shape Memory Alloys)

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10 pages, 1971 KiB

Open AccessArticle

Microstructure, Phase Transformations, and Mechanical Properties of Shape Memory Fe-Mn-V-C Austenitic Steels

by Victor Sagaradze, Sergey Afanasiev, Natalya Kataeva and Yurii Ustyugov

Metals 2023, 13(2), 248; https://doi.org/10.3390/met13020248 - 28 Jan 2023

Cited by 1 | Viewed by 1158

Abstract

The structure and mechanical properties of new dispersion-hardened Mn-(Cr)-Si-V-C steels with a shape memory effect (SME), which undergo strengthening due to the precipitation of VC carbides in a steel matrix, were analyzed. The stabilizing and the destabilizing carbide aging at different temperatures allows [...] Read more.

The structure and mechanical properties of new dispersion-hardened Mn-(Cr)-Si-V-C steels with a shape memory effect (SME), which undergo strengthening due to the precipitation of VC carbides in a steel matrix, were analyzed. The stabilizing and the destabilizing carbide aging at different temperatures allows one to control and thus adjust the desired strength characteristics (σ_0,2 = 250–880 MPa) and amount of reversible deformation (up to 2.7%). The recovery of the shape of the samples was carried out as a result of both the γ-ε transition in the course of heating after preliminary deformation in the initial austenitic state (i.e., due to the transformation of the γ to the ε phase) and the shear re-twinning of martensite in the martensitic ε phase (i.e., due to the occurrence of transformation of the ε to the twinned ε_tw phase). Full article

(This article belongs to the Special Issue Microstructure and Mechanical Behaviour of Shape Memory Alloys)

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13 pages, 3967 KiB

Open AccessArticle

Effect of the Surface Oxide Layer on Shape Memory Effect and Superelasticity of [011]-Oriented Ti-50.1Ni Single Crystals

by Yuriy I. Chumlyakov, Irina V. Kireeva, Anastasia A. Saraeva, Zinaida V. Pobedennaya and Anna V. Vyrodova

Metals 2022, 12(11), 1932; https://doi.org/10.3390/met12111932 - 11 Nov 2022

Cited by 1 | Viewed by 1163

Abstract

Effect of the surface oxide layer on the shape memory effect (SME) and superelasticity (SE) after marforming (deformation in the martensitic state, followed by annealing at 713 K for 0.5 h in an inert helium gas and in dry air) was investigated on [...] Read more.

Effect of the surface oxide layer on the shape memory effect (SME) and superelasticity (SE) after marforming (deformation in the martensitic state, followed by annealing at 713 K for 0.5 h in an inert helium gas and in dry air) was investigated on Ti-50.1Ni (at.%) single crystals, oriented along [011]-direction, under compression. Quenched [011]-oriented crystals of the Ti-50.1Ni alloy experience a one-stage B2-B19′ martensitic transformation (MT) without SE under compression. Marforming leads to a two-stage B2-R-B19′ MT and creates conditions for SE. A thin TiO₂ oxide layer of 170 nm thick was formed on the sample surface upon annealing at 713 K for 0.5 h in dry air. In [011]-oriented crystals without and with an oxide layer, maximum of the SE value reached 4%, and the SME was 2.4 and 2.6%, respectively. Appearance of an oxide layer upon annealing in dry air: (i) reduces the stresses of B2-phase by 50 MPa from M_d to 473 K; (ii) decreases Θ = dσ/dε from 6.5 GPa in crystals without an oxide layer to 2.0 GPa with an oxide layer and (iii) does not affect the SME and SE values. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Behaviour of Shape Memory Alloys)

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12 pages, 3501 KiB

Open AccessFeature PaperArticle

Effect of Aging Treatments on the Structure, Deformation Response, and R Transformation in Nanocrystalline Ti–50.9 at.% Ni Alloy

by Tamara M. Poletika, Svetlana L. Girsova, Sergey M. Bitter and Aleksander I. Lotkov

Metals 2022, 12(10), 1725; https://doi.org/10.3390/met12101725 - 14 Oct 2022

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Abstract

This paper presents the results of a transmission electron microscope study of the influence of the size, morphology, and spatial distribution of coherent Ti₃Ni₄ particles on the nature of the R transformation; the morphology of the R phase; and the [...] Read more.

This paper presents the results of a transmission electron microscope study of the influence of the size, morphology, and spatial distribution of coherent Ti₃Ni₄ particles on the nature of the R transformation; the morphology of the R phase; and the deformation response depending on the aging temperature in nanocrystalline Ti–50.9 at.% Ni alloy with a grain–subgrain structure. It has been established that with an increase in the aging temperature, the size and spatial distribution of Ti₃Ni₄ particles change from being located on dislocations at an aging temperature of 300 °C to precipitation at sub-boundaries at an aging temperature of 400 °C, 450 °C. Correspondingly, the morphology of the R phase changes from nanodomain-like to a lamellar self-accommodation structure. Studies have shown that the morphology of the R phase, in turn, affects the deformation response of the material. In the case of lamellar self-accommodation morphology, localized R transformation develops in a Lüders-like manner. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Behaviour of Shape Memory Alloys)

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18 pages, 9321 KiB

Open AccessArticle

Microstructure, Mechanical and Superelastic Properties of Ti-Zr-Nb Alloy for Biomedical Application Subjected to Equal Channel Angular Pressing and Annealing

by Vadim Sheremetyev, Mikhail Derkach, Anna Churakova, Aleksander Komissarov, Dmitry Gunderov, Georgy Raab, Vladimir Cheverikin, Sergey Prokoshkin and Vladimir Brailovski

Metals 2022, 12(10), 1672; https://doi.org/10.3390/met12101672 - 05 Oct 2022

Cited by 2 | Viewed by 1545

Abstract

Biomedical Ti-18Zr-15Nb (at.%) shape memory alloy was subjected to a low-temperature equal channel angular pressing (ECAP) at 200 °C for three passes and post-deformation annealing (PDA) in the 400–650 °C temperature range for 1 to 60 min. It was observed that ECAP led [...] Read more.

Biomedical Ti-18Zr-15Nb (at.%) shape memory alloy was subjected to a low-temperature equal channel angular pressing (ECAP) at 200 °C for three passes and post-deformation annealing (PDA) in the 400–650 °C temperature range for 1 to 60 min. It was observed that ECAP led to the formation of an inhomogeneous highly dislocated substructure of β-phase with a large number of differently oriented deformation bands containing nanograined and nano-subgrained areas. In this state, the alloy strength increased significantly, as compared to the undeformed state, but its ductility and superelasticity deteriorated appreciably. As a result of a short-term (5 min) PDA at 550–600 °C, the processes of polygonization of an entire volume of the material and recrystallization inside the deformation bands were observed. After PDA at 600 °C for 5 min, the alloy manifested a relatively high strength (UTS = 650 MPa), a satisfactory ductility (δ = 15%) and a superior superelastic behavior with a maximum superelastic recovery strain of ε_r^se_max = 3.4%. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Behaviour of Shape Memory Alloys)

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11 pages, 4514 KiB

Open AccessArticle

Mechanical Properties of the Ti_49.8Ni_50.2 Alloy after Multi-Axial Forging at 573 K

by Aleksandr Lotkov, Oleg Kashin, Victor Grishkov, Dorzhima Zhapova, Konstantin Krukovskii, Angelina Gusarenko, Natalia Girsova, Dmitrii Bobrov and Olga Kashina

Metals 2022, 12(6), 1043; https://doi.org/10.3390/met12061043 - 18 Jun 2022

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Abstract

The mechanical properties of Ti_49.8Ni_50.2 (at %) alloy under tension at room temperature are studied in dependence on the true strain (e = 1.84–9.55) specified during isothermal multi-axial forging (abc-pressing). It was found that the stress at the beginning [...] Read more.

The mechanical properties of Ti_49.8Ni_50.2 (at %) alloy under tension at room temperature are studied in dependence on the true strain (e = 1.84–9.55) specified during isothermal multi-axial forging (abc-pressing). It was found that the stress at the beginning of the pseudoyield plateau does not depend on the value of the true abc-strain. It was found that after abs-pressing, already at a true strain e = 1.84, the yield stress σ_y was 900 ± 25 MPa, which is more than twice as high as compared to σ_y in the initial state of the specimens. With a further increase in the abc-strain, the yield stress continues to increase slightly and reaches 1000 ± 25 MPa at e = 9.55. In this case, the ultimate tensile strength of the samples increases by about 15%. The strain-hardening coefficient ϴ = dσ/dε at the III (linear) stage of the σ(ε) curve has a similar dependence on e. It is shown that after abc-pressing with e from 1.84 to 9.55, the yield stress and ultimate tensile increase linearly with increasing d^−1/2 in accordance with the Hall–Petch relation, where d is the average grain–subgrain size. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Behaviour of Shape Memory Alloys)

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Review

Jump to: Research

33 pages, 18411 KiB

Open AccessReview

Influence of Heat Treatment and Deformation on the Structure, Phase Transformation, and Mechanical Behavior of Bulk TiNi-Based Alloys

by Nataliya N. Kuranova, Vladimir V. Makarov, Vladimir G. Pushin and Yurii M. Ustyugov

Metals 2022, 12(12), 2188; https://doi.org/10.3390/met12122188 - 19 Dec 2022

Cited by 6 | Viewed by 1572

Abstract

We present a brief overview of the structural and phase transformations and mechanical properties of bulk binary TiNi shape memory alloys, which demonstrate attractive commercial potential. The main goal of this work was to create a favorable microstructure of bulk alloys using both [...] Read more.

We present a brief overview of the structural and phase transformations and mechanical properties of bulk binary TiNi shape memory alloys, which demonstrate attractive commercial potential. The main goal of this work was to create a favorable microstructure of bulk alloys using both traditional and new alternative methods of thermal and thermomechanical processing. It was found that the implementation of an ultrafine-grained structure by different methods determined an unusual combination of strength, ductility, reversible deformation, reactive resistance of these alloys to subsequent tensile or torsion tests at room temperature, and, as a consequence, the highly reversible effects of the shape memory and superelasticity. It is shown that the alloys Ti_49.8Ni_50.2 and Ti_49.4Ni_50.6 are incapable of aging, and, after being subjected to ECAP, were characterized by their high strength (σ_u up to 1200 MPa) and ductility (δ up to 60–70%). A combined treatment of multi-pass rolling and HT of the Ti_49.5Ni_50.5 and Ti₄₉Ni₅₁ alloys prone to aging have provided even greater strength (σ_u up to 1400–1500 MPa) with slightly lower ductility (25–30%). The microstructure, phase composition, and martensitic transformations in Ti-Ni alloys with varying Ni concentrations ranging from 50 to 51 wt.% were investigated by TEM, SEM, and X-ray methods. The mechanical behavior of the alloys was studied during tensile and torsion tests. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Behaviour of Shape Memory Alloys)

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