Superplastic Deformation of 01420T Alloy with Initial Bimodal Grain Structure

Milaya, D.E.; Poyda, V. P.; Bryukhovetsky, V.V.; Poyda, A. V.

doi:10.15407/mfint.42.04.0511

Metallofiz. Noveishie Tekhnol.

2020

DOI: 10.15407/mfint.42.04.0511

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Superplastic Deformation of 01420T Alloy with Initial Bimodal Grain Structure

D.E. Milaya¹,

V. P. Poyda²,

V.V. Bryukhovetsky³

et al.

Abstract: Проведено механічні випробування зразків алюмінієвого стопу системи Al-Mg-Li марки 01420Т та визначено температурно-швидкісні умови, за яких зразки цього стопу з вихідною бімодальною зеренною структурою проявляють ефект надпластичності. Вивчено структурні зміни, що відбуваються в зразках дослідженого стопу під час надпластичної деформації. Встановлено, що у ході надпластичної деформації мікроструктура зразків стопу стає однорідною та ультрадрібнозернистою. В робочій частині зразків стопу 01420Т в ході надпласт… Show more

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Morphology of fibrous structures formed in the course of superplastic deformation of the 01420T alloy with the original bimodal grain structure

Poyda,

Milaya,

Poyda

et al. 2021

The Journal of v. N. Karazin Kharkiv National University, Series "Physics"

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The morphology of the fibrous structures formed in the working parts of the 01420T alloy samples with the initial bimodal grain structure, deformed to fracture under optimal conditions of superplastic deformation at a temperature Т = 520°С and flow stress σ = 4,5 MPa is investigated. The maximum elongation of specimens deformed to failure δ is 670%. It has been suggested that the specific type of fibrous structures found in the specimens of the investigated alloy 01420T probably depends on the volume of the metastable liquid-solid phase, which was concentrated in the form of inclusions at some grain boundaries and made a viscous flow during superplastic deformation, its shear viscosity , the characteristics of its surface tension, the degree of dynamic oxidation of the melt, and the kinetics of the development of this process. The final view of the fibers and their shape, likely, depends not only on the nature of the viscous flow of the liquid-solid material, but also on the process of its crystallization during the cooling of the specimen in air to room temperature after mechanical tests. It was found that in view, all fibrous structures found in the working parts of the specimens can be conditionally divided into the following: cylindrical fibers; tapered fibers; cylindrical fibers on which there is a thickening or one or more drop-like formations; ribbon-like fibers; fibers that look like stalactites or stalagmites. The reasons for the formation of cracks on ribbon-like fibers are considered. It is assumed that they were formed as a result of relaxation of internal stresses, which were not fully minimized in the course of recrystallization, which was carried out when the sample was cooled. The reasons for the formation of droplets on the fibers are considered. It has been suggested that fibrous structures similar to stalactites and stalagmites were formed from a viscous material, which, in the course of superplastic deformation, as a result of crystallization, occured in local microvolumes of fibers, gradually turned from liquid-solid to solid-liquid. This led to the fact that in the crystallized microvolume of this fiber, the viscous homogeneous flow of the material probably turned into a localized flow, which is characteristic of the plastic flow carried out as a result of displacement of dislocations in the solid phase, and leads to the formation of stalagmitic fibers.

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Morphology of fibrous structures formed in the course of superplastic deformation of the 01420T alloy with the original bimodal grain structure

Poyda,

Milaya,

Poyda

et al. 2021

The Journal of v. N. Karazin Kharkiv National University, Series "Physics"

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show abstract

The influence of the main alloying elements on the formation of the initial grain structure, on phase transformations and on structural changes that occur during superplastic deformation of alloys Al - 4.1 wt.% Mg - 0.5 wt.% Zr, 1420T, 1421, 1423

Poyda,

Mila

2022

The Journal of v. N. Karazin Kharkiv National University, Series "Physics"

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The article presents the results of research aimed at revealing the influence of the main alloying elements on the formation of the initial grain structure, on phase transformations and on structural changes that occur during superplastic deformation of several aluminum alloys. It was possible to form a homogeneous ultrafine-grained structure in samples of alloys Al - 4.1 wt.% Mg - 0.5 wt.% Zr and 1423 due to dynamic recrystallization during their superplastic deformation. It is revealed that the initial microstructure of the 1420T alloy samples is bimodal. The average grain size is approximately 5 μm, in some areas of the working part of the samples there are large elongated grains, the average size of which is approximately equal to 25 μm. The initial structure of alloy 1421 samples is fine-grained, and the initial structure of alloy 1423 samples is multi-grained and coarse-grained. Metallographic studies showed that the grain structure of samples of alloys 1420T, 1421 and 1423 increases slightly during superplastic deformation at high homologous temperatures. Cavitation accumulates in the samples and structural changes occur, which are probably associated with local melting at grain boundaries and at interphase boundaries. It was established that the presence of zirconium and scandium additions in the composition of the samples ensures the formation of an ultrafine-grained structure in them and counteracts the grain growth during superplastic flow. Magnesium and lithium, which are included in the samples of the studied alloys 1420T, 1421 and 1423, form several intermetallic phases with aluminum. These phases are part of mixtures of crystals of peritectic origin, which are localized in the form of layers between some grains. The occurrence of peritectic reactions at high homologous temperatures can be one of the reasons for the partial melting of samples of alloys 1420T, 1421, and 1423 during their superplastic deformation. Partial melting of samples of alloys 1420T, 1421 and 1423 can probably be carried out due to the presence of segregations of magnesium and lithium at the grain boundaries, which lower the melting temperature of the aluminum-based solid solution. Partial melting of samples of alloys 1420T, 1421, and 1423 during their superplastic deformation, which is performed at high homologous temperatures, leads to the formation of cells of a metastable liquid-solid phase at the grain boundaries, the viscous flow of which leads to the formation of fibrous structures due to the development of grain boundary sliding.

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Superplastic Deformation of 01420T Alloy with Initial Bimodal Grain Structure

Cited by 2 publications

References 14 publications

Morphology of fibrous structures formed in the course of superplastic deformation of the 01420T alloy with the original bimodal grain structure

Morphology of fibrous structures formed in the course of superplastic deformation of the 01420T alloy with the original bimodal grain structure

The influence of the main alloying elements on the formation of the initial grain structure, on phase transformations and on structural changes that occur during superplastic deformation of alloys Al - 4.1 wt.% Mg - 0.5 wt.% Zr, 1420T, 1421, 1423

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