Special Issue "Nanocrystalline Metals and Alloys"

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A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: closed (30 November 2011)

Special Issue Editor

Guest Editor
Dr. Pasquale Daniele Cavaliere (Website)

Department of Innovation Engineering University of Salento, Lecce 73100, Italy
Interests: constitutive equations for the forming and in service conditions; damage prevision in metals and alloys; superplastic forming of Light alloys; fatigue properties of materials; nonostructured materials

Special Issue Information

Dear Colleagues,

The strength of metals and alloys is strongly influenced by grain size with materials in the nanocrystalline regime characterized by superior yield and fracture strength, improved wear resistance and superplasticity observed at relatively low temperatures and high strain rates as compared with their microcrystalline counterparts. This has led to increased attention towards charactering their mechanical properties and deformation mechanism, these work summarized in recent review articles. The current attention to the potential industrial application of nanopolycrystals leads to the necessity of deep investigations of their mechanical physical and chemical properties both in static and dynamic conditions. Several laboratory-scale processing techniques are currently available to produce nanocrystalline (nc<100nm) and ultra-fine crystalline (ufc<1mm) materials. Today, the materials community realizes that the hopes for ultra-strong and ductile bulk nanocrystalline materials have not materialized yet. The reduction of the grain size down to the nanometer regime opened new and fascinating avenues for research in several aspects of material science, including mechanical properties. In polycrystalline metals with grain sizes in the micron range, the traditional view of plasticity is based on dislocation activity: dislocation sources are active within a grain, dislocations repel each other and they distribute themselves over available area within the slip plane delimited by the grain boundaries. Additionally, dislocations are attracted to the boundaries of the slip plane as a result of image forces and consequently, their distribution peaks close to the boundaries in the so-called pile-up effect. When the stress field resulting from the addition of individual dislocation contributions reaches some critical value, it activates sources in neighboring grains.

As a result of all this, the material becomes harder to deformScientifically, the study of nanocrystalline materials is of great interest because the potential breakdown of classical scaling laws and the accompanying need for new materials physics in the nanostructured state. Understanding the basic deformation mechanisms and the key microstructural parameters that influence the materials macroscopic behavior at such small grain size, the way to the development of ductile and high performance nanocrystalline structures is open. At a nanometric scale, different mechanisms take place during monotonic or cyclic loading respect to the microcrystalline metals; The nanocrystalline metals and alloys contain a very high fraction of grain boundary volume; therefore grain boundaries and their interactions with crystal defects play a significant role in the deformation of these materials. Advances in the processing alloys along with the precipitous rise in the sophistication of routines, commonly available tools capable of characterizing materials with force, displacement and spatial resolution smaller and smaller, permit to obtain scientific data very precise on the mechanical response on nanocrystalline materials. Large improvements in computer hardware and software permit the simulation of the structures and deformation of nanostructures helping scientists in the well-understanding of the processes on nanoscale.

The main goal of the special issue “Nanocrystalline metals and alloys” is to represent a miliar stone in the field of nanostructured materials from synthesis, to processing to industrial application.

Dr. Pasquale Daniele Cavaliere
Guest Editor

Keywords

  • nanostructured materials
  • syntesis
  • production
  • deformation
  • elasticity
  • plasticity
  • applications
  • future prospective

Published Papers (3 papers)

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Research

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Open AccessArticle Crack Propagation in Honeycomb Cellular Materials: A Computational Approach
Metals 2012, 2(1), 65-78; doi:10.3390/met2010065
Received: 29 November 2011 / Revised: 13 January 2012 / Accepted: 2 February 2012 / Published: 13 February 2012
Cited by 3 | PDF Full-text (2493 KB) | HTML Full-text | XML Full-text
Abstract
Computational models based on the finite element method and linear or nonlinear fracture mechanics are herein proposed to study the mechanical response of functionally designed cellular components. It is demonstrated that, via a suitable tailoring of the properties of interfaces present in [...] Read more.
Computational models based on the finite element method and linear or nonlinear fracture mechanics are herein proposed to study the mechanical response of functionally designed cellular components. It is demonstrated that, via a suitable tailoring of the properties of interfaces present in the meso- and micro-structures, the tensile strength can be substantially increased as compared to that of a standard polycrystalline material. Moreover, numerical examples regarding the structural response of these components when subjected to loading conditions typical of cutting operations are provided. As a general trend, the occurrence of tortuous crack paths is highly favorable: stable crack propagation can be achieved in case of critical crack growth, whereas an increased fatigue life can be obtained for a sub-critical crack propagation. Full article
(This article belongs to the Special Issue Nanocrystalline Metals and Alloys)
Open AccessArticle Evolution of Morphology and Microstructure in Electrodeposited Nanocrystalline Al–Mg Alloy Dendrites
Metals 2011, 1(1), 3-15; doi:10.3390/met1010003
Received: 8 August 2011 / Revised: 23 August 2011 / Accepted: 29 August 2011 / Published: 5 September 2011
PDF Full-text (1143 KB) | HTML Full-text | XML Full-text
Abstract
Nanocrystalline Al–Mg dendrites were fabricated through galvanostatic electrodeposition. Initially feather-like morphology was formed exhibiting morphological evolution to smooth globules at its tips. With eventual deposition, rough globules formed over the smooth ones. The feather-like and smooth globules possessed supersaturated face centered cubic [...] Read more.
Nanocrystalline Al–Mg dendrites were fabricated through galvanostatic electrodeposition. Initially feather-like morphology was formed exhibiting morphological evolution to smooth globules at its tips. With eventual deposition, rough globules formed over the smooth ones. The feather-like and smooth globules possessed supersaturated face centered cubic (fcc)–Al(Mg) phase with ~7 and ~20 at.% Mg respectively. The rough globules contained hexagonal close packed (hcp)–Mg(Al) phase with ~80 at.% Mg. Microstructural examinations revealed that the feather-like and rough globules possessed grain sizes of ~42 ± 15 and ~36 ± 12 nm respectively. The region, which exhibited morphological evolution from feather-like to smooth globules, possessed ~16 ± 7 nm grain size. The observed microstructural and compositional features were attributed to the local current density values. The formation of the Al–Mg dendrites is discussed in this paper. Full article
(This article belongs to the Special Issue Nanocrystalline Metals and Alloys)
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Review

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Open AccessReview Nanocrystalline Metal Hydrides Obtained by Severe Plastic Deformations
Metals 2012, 2(1), 22-40; doi:10.3390/met2010022
Received: 30 November 2011 / Revised: 27 December 2011 / Accepted: 27 December 2011 / Published: 10 January 2012
Cited by 10 | PDF Full-text (2280 KB) | HTML Full-text | XML Full-text
Abstract
It has recently been shown that Severe Plastic Deformation (SPD) techniques could be used to obtain nanostructured metal hydrides with enhanced hydrogen sorption properties. In this paper we review the different SPD techniques used on metal hydrides and present some specific cases [...] Read more.
It has recently been shown that Severe Plastic Deformation (SPD) techniques could be used to obtain nanostructured metal hydrides with enhanced hydrogen sorption properties. In this paper we review the different SPD techniques used on metal hydrides and present some specific cases of the effect of cold rolling on the hydrogen storage properties and crystal structure of various types of metal hydrides such as magnesium-based alloys and body centered cubic (BCC) alloys. Results show that generally cold rolling is as effective as ball milling to enhance hydrogen sorption kinetics. However, for some alloys such as TiV0.9Mn1.1 alloy ball milling and cold rolling have detrimental effect on hydrogen capacity. The exact mechanism responsible for the change in hydrogenation properties may not be the same for ball milling and cold rolling. Nevertheless, particle size reduction and texture seems to play a leading role in the hydrogen sorption enhancement of cold rolled metal hydrides. Full article
(This article belongs to the Special Issue Nanocrystalline Metals and Alloys)

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