Superplastic‐Like Behavior and Enhanced Strength of a Two‐Phase Titanium Alloy with Ultrafine Grains

D’yakonov, G. S.; Рааб, Г. И.; Pesin, Mikhail V.; Polyakov, A.; Semenova, Irina P.; Valiev, Ruslan Z.

doi:10.1002/adem.202101592

Cited by 5 publications

(3 citation statements)

References 28 publications

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“…At the same time, the creation of a finished product normally implies several process operations, one of which is most often is shape forming by compression (die forging), which is conducted at rather high temperatures [ 11 , 12 , 13 ]. However, as noted by many researchers, UFG materials exhibit a higher technological plasticity due to the occurrence of the superplasticity effect at lower temperatures than in the case of standard deformation treatments [ 14 , 15 , 16 ]. As is widely known [ 11 , 17 , 18 ], products manufactured under the superplastic flow of a material exhibit homogeneity of the micro- and macrostructure in the whole product volume, which contributes to a high reliability of the product and a uniform distribution of stress in the material’s volume.…”

Section: Introductionmentioning

confidence: 99%

Superplastic Behavior and Microstructural Features of the VT6 Titanium Alloy with an Ultrafine-Grained Structure during Upsetting

D’yakonov¹,

Stotskiy²,

Modina³

et al. 2023

Materials

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In this paper, the superplastic behavior of the two-phase titanium alloy VT6 with an ultrafine-grained (UFG) structure produced by equal-channel angular pressing is examined. The deformation of specimens with a UFG structure was performed by upsetting in a temperature range of 650–750 °C and strain rate range of 1 × 10−4–5 × 10−1 s−1. Under these conditions, an increased strain-rate sensitivity coefficient m was observed. The calculation of apparent activation energy showed values in a range of 160–200 kJ/mol while the superplastic flow of the VT6 alloy was occurring. When superplastic behavior (SPB) was impeded, the energy Q grew considerably, indicating a change in mechanism from grain-boundary sliding (GBS) to bulk diffusion. A change in temperature and strain rate influenced the development of superplastic flow and the balance of relaxation processes. Microstructural analysis shows that the UFG state is preserved at upsetting temperatures of 650 and 700 °C. A decrease in strain rate and/or an increase in upsetting temperature promoted a more active development of recrystallization and grain growth, as well as α2-phase formation. In a certain temperature and strain-rate range of the UFG VT6 alloy, α2-phase plates were found, the formation of which was controlled by diffusion. The effect of the α2-phase on the alloy’s mechanical behavior is discussed.

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Section: Introductionmentioning

confidence: 99%

Superplastic Behavior and Microstructural Features of the VT6 Titanium Alloy with an Ultrafine-Grained Structure during Upsetting

D’yakonov¹,

Stotskiy²,

Modina³

et al. 2023

Materials

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“…It is well documented that some novel grain refinement techniques based on imposing very high strains to the material via introduction of severe plastic deformation (SPD) provides the capability of decreasing grain sizes down to micron or sub-micron range. Equal channel angular pressing (ECAP), 14,15) high pressure torsion (HPT), 16,17) friction stir processing (FSP), 18,19) accumulative roll bonding (ARB) 20) and multi-axial forging (MAF) 21) are some of the main SPD techniques. Principles of most commonly used SPD methods and historical development of UFG materials besides with the main properties of nanostructured SPD materials were wellexplained in Refs.…”

Section: Introductionmentioning

confidence: 99%

An Overview of the Principles of Low-Temperature Superplasticity in Metallic Materials Processed by Severe Plastic Deformation

Demirtas

Pürçek

2023

Mater. Trans.

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Low-temperature superplasticity (LTS) is crucial to reduce manufacturing cost and to enhance the applications of superplastic forming. It is well known that grain refinement is the key point to decrease the temperature at which superplasticity is attained. Therefore, ultrafine-grained (UFG) materials have become attractive for achieving LTS. Severe plastic deformation (SPD) techniques provide abnormal grain refinement, and thus they have been used to achieve LTS in metallic materials. This paper overviews and examines the reports of LTS in the severely-deformed metallic materials. It provides fundamentals of grain refinement via different SPD techniques in various classes of metallic materials including Al-, Mg-, and Ti-based alloys. It also gives a brief summary about the effect of microstructural requirements on LTS with an emphasis on grain size, type and chemical composition of grain boundaries and microstructural alteration during the superplastic deformation. In the last section of the manuscript, the main deformation mechanism of LTS were also explained.

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“…As a result, the mechanical properties of ultrafine-grained (UFG) materials are significantly improved, compared to those of coarse-grained materials. Several UFG materials, including aluminum alloys, for instance, were found to exhibit superplastic behavior, enhanced flow stress, and high Vickers microhardness [22][23][24]. Mabuchi and Higashi [25] investigated the mechanical properties of a relatively low-purity Al (99.5%) and a high-purity Al (99.9999%) deformed using ECAP at room temperature.…”

Section: Introductionmentioning

confidence: 99%

Grain Refinement and Strengthening of an Aluminum Alloy Subjected to Severe Plastic Deformation through Equal-Channel Angular Pressing

Korchef

Souid

2023

Crystals

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In the present study, the microstructure, mechanical properties, and stored energy of an aluminum alloy containing iron-rich fine precipitates, subjected to severe plastic deformation through equal-channel angular pressing (ECAP), were investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. Up to four passes through ECAP resulted in significant nanometer-scale grain refinement, as well as the accumulation of lattice defects, such as dislocations and mesoscopic shear planes. This resulted in a noticeable enhancement in the Vickers microhardness and the flow stress after ECAP. Differential scanning calorimetry results showed that the ECAP’ed material exhibited two exothermal peaks at 222 ± 2 °C and 362 ± 2 °C, with total thermal effects of ΔH = 4.35 and 6.5 J/g, respectively. Slight increases in the ECAP’ed material microhardness and flow stress were observed at 200 °C. The heat release, at a relatively low temperature, and the slight improvement in the mechanical properties were attributed to the evolution of low- and high-angle misorientation, with the strain and the pinning of tangled dislocation caused by the existing fine particles. The second peak was attributed to grain growth, resulting in a significant softening of the material.

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Superplastic‐Like Behavior and Enhanced Strength of a Two‐Phase Titanium Alloy with Ultrafine Grains

Cited by 5 publications

References 28 publications

Superplastic Behavior and Microstructural Features of the VT6 Titanium Alloy with an Ultrafine-Grained Structure during Upsetting

Superplastic Behavior and Microstructural Features of the VT6 Titanium Alloy with an Ultrafine-Grained Structure during Upsetting

An Overview of the Principles of Low-Temperature Superplasticity in Metallic Materials Processed by Severe Plastic Deformation

Grain Refinement and Strengthening of an Aluminum Alloy Subjected to Severe Plastic Deformation through Equal-Channel Angular Pressing

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