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Metals
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Ultrafine-Grained Metals and Alloys
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Ultrafine-Grained Metals and Alloys

A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Crystallography and Applications of Metallic Materials".

Deadline for manuscript submissions: closed (31 October 2023) | Viewed by 5528

Special Issue Editors

Prof. Dr. Mikhail Yu. Gutkin

E-Mail Website
Guest Editor
1. Institute for Problems in Mechanical Engineering, Russian Academy of Sciences, 199178 St. Petersburg, Russia
2. Institute of Advanced Data Transfer Systems, ITMO University, 197101 St. Petersburg, Russia
3. Department of Mechanics and Control Processes, Peter the Great St. Petersburg Polytechnic University, 194021 St. Petersburg, Russia

Interests: theory of defects; micromechanics of strength and plasticity; ultrafine-grained metals; nanostructured solids; semiconductor nanoheterostructures
Prof. Dr. Tatiana S. Orlova

E-Mail Website
Guest Editor
1. Division of Solid State Physics, Ioffe Institute, 194021 St. Petersburg, Russia
2. Institute of Advanced Data Transfer Systems, ITMO University, 197101 St. Petersburg, Russia
Interests: ultrafine-grained metals and alloys; ceramic materials; hybrid carbon structures; severe plastic deformation; nanostructures; microstructure; defect structure; boundaries; strength; plasticity; electrical and magnetic properties

Special Issue Information

Dear Colleagues,

Over the last three decades, the research and development in the field of ultrafine-grained (UFG) metals and alloys has remained one of the hottest topics in materials science, solid-state physics, chemistry and mechanics of materials. Starting from the first idea to increase the strength of polycrystalline metals by diminishing their grain size down to a submicron scale, the research later focused on attempts to combine high-strength and required plasticity in one UFG metal. In recent years, researchers have looked for the most effective routes of preparing UFG metals and alloys suitable for the conditions of mass industrial production, as well as new areas of their potential application, in particular, those where the combination of superior functional and good structural properties is required. Cooperative efforts undertaken by different means, including experiments, computer simulations and theoretical modelling, have allowed for the imagination of a wide variety of deformation and fracture processes responsible for the mechanical behaviour of UFG metals and alloys on different temporal and spatial scales. Thanks to these results, new types of UFG metals and alloys have been produced, characterized and tested in applications, such as, for example, UFG materials with specially designed grain boundaries, doping element segregations and precipitates, etc., with no doubt that novel types of UFG metals and alloys are currently being developing and/or likely to appear in the nearest future.

To examine and estimate the state of the art in the field of the research and development of ultrafine-grained metals and alloys, we invite you to present your articles in this Special Issue of the open access journal Metals devoted to different aspects of fabrication, thermo-mechanical treatment, characterization, testing and studying the deformation behaviour and different functional properties of these materials.

Prof. Dr. Mikhail Yu. Gutkin
Prof. Dr. Tatiana S. Orlova
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Metals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • ultrafine-grained metals and alloys
  • severe plastic deformation
  • thermo-mechanical treatment
  • non-equilibrium grain boundaries
  • grain-boundary segregations and precipitates
  • dislocation structures
  • strength
  • plasticity
  • electric conductivity
  • magnetic properties

Published Papers (5 papers)

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Research

16 pages, 10248 KiB  
Article
Effect of Deformation-Induced Plasticity in Low-Alloyed Al-Mg-Zr Alloy Processed by High-Pressure Torsion
by Tatiana S. Orlova, Aydar M. Mavlyutov, Dinislam I. Sadykov, Nariman A. Enikeev and Maxim Yu. Murashkin
Metals 2023, 13(9), 1570; https://doi.org/10.3390/met13091570 - 7 Sep 2023
Cited by 2 | Viewed by 793
Abstract
The influence of additional deformation heat treatments (DHTs), implemented by two regimes: (1) annealing and small additional deformation by high-pressure torsion (HPT) at room temperature (RT) and (2) HPT at elevated temperature to 10 turns and small additional HPT at RT, has been [...] Read more.
The influence of additional deformation heat treatments (DHTs), implemented by two regimes: (1) annealing and small additional deformation by high-pressure torsion (HPT) at room temperature (RT) and (2) HPT at elevated temperature to 10 turns and small additional HPT at RT, has been studied on the microstructure, mechanical properties and electrical conductivity of ultrafine-grained (UFG) Al-0.53Mg-0.27Zr (wt.%) alloy structured by HPT to 10 turns at RT. As is shown, both types of additional DHT lead to a substantial increase in plasticity (2–5 times) while maintaining high electrical conductivity (~53% IACS) and strength comprising 75–85% of the value in the pre-DHT state of the UFG alloy. The possible physical reasons for the revealed changes in the physical and mechanical properties are analyzed. Comparison of the strength and plasticity changes with the microstructure evolution after DHT of both types indicates that the increase in the density of introduced grain boundary dislocations is the most probable factor providing a tremendous increase in plasticity while maintaining a high level of strength in the UFG alloy under study. An outstanding combination of high strength (370 MPa), high elongation to failure (~15%) and significant electrical conductivity (~53% IACS) was achieved for the Al-Mg-Zr alloy. This combination of properties exceeds those obtained to date for this system, as well as for a number of other commercial conductor alloys based on the Al-Zr system. Full article
(This article belongs to the Special Issue Ultrafine-Grained Metals and Alloys)
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11 pages, 2028 KiB  
Article
Structure Refinement and Bauschinger Effect in fcc and hcp Metals
by Vladimir V. Stolyarov
Metals 2023, 13(7), 1307; https://doi.org/10.3390/met13071307 - 21 Jul 2023
Viewed by 852
Abstract
Although the Bauschinger effect has been investigated in some detail in various materials, the number of articles on the effect of grain size is extremely limited, and in current nanostructured materials it is practically absent. Since such materials are considered as promising for [...] Read more.
Although the Bauschinger effect has been investigated in some detail in various materials, the number of articles on the effect of grain size is extremely limited, and in current nanostructured materials it is practically absent. Since such materials are considered as promising for structural applications, it is important to understand their mechanical behavior under conditions of changing the direction of deformation, and, therefore, it is necessary to study the Bauschinger effect and its dependence on grain size. The Bauschinger effect was investigated by a single exemplary method for tensile compression of commercially pure hcp titanium and fcc copper, with different grain sizes in the range from hundreds of microns to hundreds of nanometers. The change in grain size was performed by structure refinement by the method of severe plastic deformation using equal-channel angular pressing and subsequent annealing. It has been established that, in both materials, the Bauschinger effect increases with a decrease in grain size, the degree of permanent strain and the duration of exposure between forward and reverse deformation. The signs of the Bauschinger parameter in copper and titanium are opposite. The relationship between the Bauschinger effect and the nature of strain hardening in titanium and softening in copper in the ultrafine-grained state is discussed. Full article
(This article belongs to the Special Issue Ultrafine-Grained Metals and Alloys)
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11 pages, 1372 KiB  
Article
Modeling the Effect of Grain Boundary Segregations on the Fracture Toughness of Nanocrystalline and Ultrafine-Grained Alloys
by Alexander G. Sheinerman
Metals 2023, 13(7), 1295; https://doi.org/10.3390/met13071295 - 19 Jul 2023
Cited by 2 | Viewed by 768
Abstract
A theoretical two-dimensional (2D) model is proposed that describes the effect of grain boundary (GB) segregations on the fracture toughness of nanocrystalline or ultrafine-grained alloys. It is shown that GB segregations can lead to crack curvature, providing both crack surface roughness and crack [...] Read more.
A theoretical two-dimensional (2D) model is proposed that describes the effect of grain boundary (GB) segregations on the fracture toughness of nanocrystalline or ultrafine-grained alloys. It is shown that GB segregations can lead to crack curvature, providing both crack surface roughness and crack deflection near the crack tip. Within the model, the growth of cracks along GBs under the action of a tensile load is considered. The effects of brittle GB segregations on the crack surface roughness and crack deflection near the crack tip are analyzed, and the associated increase in the fracture toughness of the material is calculated. It is shown that toughening can be achieved if segregations are very brittle and occupy a moderate proportion of GBs. In particular, a sufficiently large (up to 50%) fraction of GBs containing very brittle segregations can increase the fracture toughness by 30–35%. The results of the model can be applied to thin nanocrystalline or ultrafine-grained films. Full article
(This article belongs to the Special Issue Ultrafine-Grained Metals and Alloys)
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19 pages, 10837 KiB  
Article
Towards Balanced Strength and Plasticity in Graphene-Nickel Composites: The Role of Graphene, Bimodal Metal Powder and Processing Conditions
by Olga Yu. Kurapova, Ivan V. Smirnov, Ivan Yu. Archakov, Chao Chen and Vladimir G. Konakov
Metals 2023, 13(6), 1037; https://doi.org/10.3390/met13061037 - 29 May 2023
Viewed by 1241
Abstract
Due to their higher strength and lighter weight compared to conventional metals, graphene-nickel (Gr-Ni) composites have recently gained growing interest for use in the automotive and aerospace industries. Homogeneous Gr dispersion, the metal powder dispersity and processing conditions play a key role in [...] Read more.
Due to their higher strength and lighter weight compared to conventional metals, graphene-nickel (Gr-Ni) composites have recently gained growing interest for use in the automotive and aerospace industries. Homogeneous Gr dispersion, the metal powder dispersity and processing conditions play a key role in obtaining the desired grain size distribution, an amount of high angle grain boundaries thus reaching the desired balance between strength and plasticity of the composite. Here, we report an approach to fabricating graphene-nickel composites with balanced strength and ductility through the microstructure optimization of the nickel matrix. A graphite platelets (GP) content of 0.1–1 wt.% was used for the optimization of the mechanical properties of the material. In situ, conversion GP-to-Gr was performed during the milling step. This paper discusses the effect of bimodal nano- and micro-sized Ni (nNi and mNi) on the mechanical properties and microstructure of Gr-Ni composites synthesized using a modified powder metallurgy approach. Specimens with varied nNi:mNi ratios were produced by two-step compaction and investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, electron back-scattered diffraction (EBSD) and nanoindentation. The best combination of ultimate tensile strength (UTS), yield limit (YL), elongation and hardness were obtained for 100nNi and 50nNi matrices, and the best composites were those with 0.1% graphene. The addition of more than 0.5 wt.% GP to the nickel matrix induces the fracture mechanism change from tensile to brittle fracture. Dedicated to the 300th anniversary of the St. Petersburg University Foundation. Full article
(This article belongs to the Special Issue Ultrafine-Grained Metals and Alloys)
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17 pages, 15064 KiB  
Article
Influence of Heat Treatment and High-Pressure Torsion on Phase Transformations in TiZrHfMoCr High-Entropy Alloy
by Alena Gornakova, Boris Straumal, Alexei Kuzmin, Alexander Tyurin, Elena Chernyaeva, Alexander Druzhinin, Natalia Afonikova and Gregory Davdian
Metals 2023, 13(6), 1030; https://doi.org/10.3390/met13061030 - 27 May 2023
Cited by 3 | Viewed by 1426
Abstract
The study focused on a 21.99 at.%Ti–22.49 at.%Zr–20.35 at.%Hf–17.45 at.%Mo–17.73 at.%Cr). Analytical techniques such as X-ray diffraction, scanning electron microscopy as well as X-ray absorption spectroscopy were employed to investigate the alloy’s structure, phase transformations, and properties. The alloy in the as-cast state [...] Read more.
The study focused on a 21.99 at.%Ti–22.49 at.%Zr–20.35 at.%Hf–17.45 at.%Mo–17.73 at.%Cr). Analytical techniques such as X-ray diffraction, scanning electron microscopy as well as X-ray absorption spectroscopy were employed to investigate the alloy’s structure, phase transformations, and properties. The alloy in the as-cast state contained three phases, namely the body-centred cubic (A2) phase, hexagonal Laves phase (C14), and cubic Laves phase (C15). The alloy has been annealed for a long time at different temperatures. It led to the disappearance of the hexagonal Laves phase, leaving behind two primary phases, namely the cubic Laves phase (C15) and the body-centered cubic phase (A2). At 1200 °C, the A2 phase almost disappeared, resulting in a practically single-phase sample. After a high-pressure torsion (HPT) treatment, the hexagonal Laves phase disappeared entirely, while the A2 and C15 phases remained. The grain size of the A2 and C15 phases was refined after HPT and grains were elongated, and their configuration resembled a layered structure. The high hardness of the A2 and C15 + C14 phases accounted for this behavior. The lattice parameters in the A2 and C15 phases after HPT treatment approached those observed after prolonged annealing at 1000 °C, indicating that the composition of these phases after short-term high-pressure torsion at ambient temperature is equivalent to the composition of these phases after long tempering at 1000 °C. The rate of diffusion-like mass transfer during severe plastic deformation was estimated to be many orders of magnitude higher than that for conventional bulk diffusion at the HPT treatment temperature and similar to that at elevated temperatures above 1000 °C. X-ray absorption spectroscopy results obtained at K-edges of Ti, Cr, Zr, and Mo as well as at the L3-edge of Hf indicated that the local environment around metal atoms before HPT was similar to that after HPT. However, the static disorder increased after HPT, which could be attributed to an increased specific amount of metal atoms in the disordered grain boundary layers after HPT-driven grain refinement. Full article
(This article belongs to the Special Issue Ultrafine-Grained Metals and Alloys)
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