Alloys

14 pages, 4132 KiB

Open AccessArticle

Mechanical Properties of Al–Mg–Si Alloys (6xxx Series): A DFT-Based Study

by Kipkorir Kirui Pius, Nicholas O. Ongwen, Maxwell Mageto, Victor Odari and Francis Magiri Gaitho

Alloys 2023, 2(3), 213-226; https://doi.org/10.3390/alloys2030015 - 13 Sep 2023

Cited by 4 | Viewed by 2214

Al–Mg–Si alloys are used in aircraft, train, and car manufacturing industries due to their advantages, which include non-corrosivity, low density, relatively low cost, high thermal and electrical conductivity, formability, and weldability. This study investigates the bulk mechanical properties of Al–Mg–Si alloys and the [...] Read more.

Al–Mg–Si alloys are used in aircraft, train, and car manufacturing industries due to their advantages, which include non-corrosivity, low density, relatively low cost, high thermal and electrical conductivity, formability, and weldability. This study investigates the bulk mechanical properties of Al–Mg–Si alloys and the influence of the Si/Mg ratio on these properties. The Al cell was used as the starting structure, and then nine structures were modeled with varying percentages of aluminium, magnesium, and silicon. Elastic constant calculations were conducted using the stress–strain method as implemented in the quantum espresso code. This study found that the optimum properties obtained were a density of 2.762 g/cm³, a bulk modulus of 83.3 GPa, a shear modulus of 34.4 GPa, a Vickers hardness of 2.79 GPa, a Poisson’s ratio of 0.413, a Pugh’s ratio of 5.42, and a yield strength of 8.38 GPa. The optimum Si/Mg ratio was found to be 4.5 for most of the mechanical properties. The study successfully established that the Si/Mg ratio is a critical factor when dealing with the mechanical properties of the Al–Mg–Si alloys. The alloys with the optimum Si/Mg ratio can be used for industrial applications such as plane skins and mining equipment where these properties are required. Full article

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29 pages, 854 KiB

Open AccessReview

A Perspective of the Design and Development of Metallic Ultra-High Temperature Materials: Refractory Metal Intermetallic Composites, Refractory Complex Concentrated Alloys and Refractory High Entropy Alloys

by Panos Tsakiropoulos

Alloys 2023, 2(3), 184-212; https://doi.org/10.3390/alloys2030014 - 30 Aug 2023

Cited by 1 | Viewed by 2416

Abstract

The paper is a personal perspective on the design of metallic ultra-high temperature materials (UHTMs). Specifically, the alloy design “landscape” of metallic UHTMs was considered from the viewpoint of the alloy design methodology NICE. The concepts of synergy, entanglement and self-regulation and their [...] Read more.

The paper is a personal perspective on the design of metallic ultra-high temperature materials (UHTMs). Specifically, the alloy design “landscape” of metallic UHTMs was considered from the viewpoint of the alloy design methodology NICE. The concepts of synergy, entanglement and self-regulation and their significance for alloy design/development were discussed. The risks, ecological challenges and material-environment interactions associated with the development of metallic UHTMs were highlighted. The “landscape” showed that beneath the complexities of alloy design lies an elegant and powerful unity of specific parameters that link logically and that progress can be made by recognising those interrelationships between parameters that generate interesting, diverse, and complex alloys. Full article

(This article belongs to the Collection Feature Paper Collection of Advanced Research on Alloys)

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16 pages, 19582 KiB

Open AccessFeature PaperArticle

On the Influence of Volumetric Energy Density and Inter-Layer Time on the Material Properties of Case-Hardening Steels

by Dominic Bartels, Moritz Elias Albert, Florian Nahr and Michael Schmidt

Alloys 2023, 2(3), 168-183; https://doi.org/10.3390/alloys2030013 - 25 Aug 2023

Viewed by 985

Abstract

Case-hardening steels are gaining increasing interest in the field of laser powder bed fusion (PBF-LB/M) due to their excellent weldability. In combination with post-process carburization heat treatment, the surface properties can be improved to generate high-strength products. When manufacturing larger products by means [...] Read more.

Case-hardening steels are gaining increasing interest in the field of laser powder bed fusion (PBF-LB/M) due to their excellent weldability. In combination with post-process carburization heat treatment, the surface properties can be improved to generate high-strength products. When manufacturing larger products by means of PBF-LB/M, the in situ heat accumulation and the altered cooling rates affect the resulting material properties. Therefore, the fabrication of larger products requires an understanding on the influencing factors that affect the material properties. This work investigates the effect of different volumetric energy densities (VED) on the resulting microstructural and mechanical properties. It is found that the hardness decreases continuously along the build direction. The gradient depends on the applied energy and is stronger for higher energy inputs due to heat accumulation and lowered cooling rates. Furthermore, countering strategies are investigated to avoid process-specific hardness reduction along the build direction. This includes a reduced number of parts within the build job as well as a modified inter-layer time (ILT) between consecutive layers of the specimen. Applying a moderate inter-layer time helps to counter process-specific overheating, which is indicated by an almost homogeneous material hardness and melt pool size along the build direction. Full article

(This article belongs to the Special Issue Design of New Metallic Alloys for AM)

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11 pages, 1376 KiB

Open AccessArticle

Production of Zirconium-Niobium Alloys for Nuclear Reactors Fuel Rods via SHS Process

by Anatoly Mukhachev, Dmytro Yelatontsev and Olena Kharytonova

Alloys 2023, 2(3), 157-167; https://doi.org/10.3390/alloys2030012 - 02 Aug 2023

Viewed by 1437

Abstract

This article presents the results of studies of the self-propagating high-temperature synthesis (SHS) for obtaining zirconium alloys with niobium by the method of calcium-thermal reduction of nuclear-grade zirconium tetrafluoride in the presence of niobium powder. The optimal heating temperature of the initial charge [...] Read more.

This article presents the results of studies of the self-propagating high-temperature synthesis (SHS) for obtaining zirconium alloys with niobium by the method of calcium-thermal reduction of nuclear-grade zirconium tetrafluoride in the presence of niobium powder. The optimal heating temperature of the initial charge and the methods of charge mixture with different calcium content were determined. The safety of the SHS process is ensured by the formation of an optimal combustion front of the mixture to remove the released high-pressure gases. A setup for the furnace reduction of zirconium alloys with charge preheating, discharge of molten products into molds of various designs, and control of the time and rate of slag and alloy crystallization has been tested. The required performance of the installation, the degree of transition of zirconium from salt into the alloy, and the purity, structure, and uniformity of the alloy were achieved. Full article

(This article belongs to the Collection Feature Paper Collection of Advanced Research on Alloys)

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9 pages, 1956 KiB

Open AccessArticle

Nature and Regularities of the Orthorhombic α″-Phase Formation in Binary Titanium Alloys

by Arkadiy V. Dobromyslov

Alloys 2023, 2(3), 148-156; https://doi.org/10.3390/alloys2030011 - 11 Jul 2023

Cited by 2 | Viewed by 1043

Abstract

A systematic study of the phase composition of quenched binary titanium alloys with d-metals of groups 5–11 from periods four to six was carried out using the methods of X-ray diffraction analysis. It was found that the formation of the orthorhombic α″-phase [...] Read more.

A systematic study of the phase composition of quenched binary titanium alloys with d-metals of groups 5–11 from periods four to six was carried out using the methods of X-ray diffraction analysis. It was found that the formation of the orthorhombic α″-phase depends on the position of the alloying metal in the periodic table. The formation of the α″-phase occurs only in the systems Ti-V, Ti-Nb, Ti-Mo, Ti-Ru, Ti-Ta, Ti-W, Ti-Re, Ti-Os and Ti-Ir, and in other systems, it does not occur. It was found that the critical parameter for the formation of the α″-phase is the difference in the size of titanium atoms and those of the alloying metal {(r_Ti − r_Me)/r_Ti 100%}. The formation of the α″-phase occurs only in systems where this value is lower than 9 at.%. Full article

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8 pages, 2857 KiB

Open AccessArticle

Spectral Visualization of Alloy Reactions during Laser Melting

by Joerg Volpp, Himani Naesstroem, Lisanne Wockenfuss, Malte Schmidt and Knut Partes

Alloys 2023, 2(3), 140-147; https://doi.org/10.3390/alloys2030010 - 04 Jul 2023

Viewed by 985

Abstract

Laser materials processing includes rapid heating to possibly high temperatures and rapid cooling of the illuminated materials. The material reactions can show significant deviations from equilibrium processing. During processing of complex materials and material combinations, it is mainly unknown how the materials react [...] Read more.

Laser materials processing includes rapid heating to possibly high temperatures and rapid cooling of the illuminated materials. The material reactions can show significant deviations from equilibrium processing. During processing of complex materials and material combinations, it is mainly unknown how the materials react and mix. However, it is important to know which chemical elements or compounds are present in the material to define the alloy. In addition, their distribution after rapid cooling needs to be better understood. Therefore, such alloy changes at rapid heating induced by laser illumination were created as pre-placed and pre-mixed powder nuggets. The energy input and the material ratio between the powder components were varied to identify characteristic responses. For the detection of reaction durations and mixing characteristics, the vapor plume content was assumed to contain the necessary information. Spectral measurements of the plume were used to identify indicators about process behaviors. It was seen that the spectral data give indications about the chemical reactions in the melt pool. The reactions of iron ore components with aluminum seem to require laser illumination to finish completely, although the thermite reaction should maintain the chemical reaction, likely due to the required melt mixing that enables the interaction of the reacting partners at all. Full article

(This article belongs to the Special Issue Design of New Metallic Alloys for AM)

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18 pages, 2391 KiB

Open AccessArticle

Fracturing of Solids as a Thermodynamic Process

by Mark Petrov

Alloys 2023, 2(3), 122-139; https://doi.org/10.3390/alloys2030009 - 30 Jun 2023

Viewed by 804

Abstract

Instead of a number of different approaches or a formal description of experimental data, a unified approach is proposed to consider failure and deformation as thermodynamic processes. Mathematical modeling of the processes is carried out using rheological models of the material. Parametric identification [...] Read more.

Instead of a number of different approaches or a formal description of experimental data, a unified approach is proposed to consider failure and deformation as thermodynamic processes. Mathematical modeling of the processes is carried out using rheological models of the material. Parametric identification of structural models is carried out using minimal necessary experiments. Based on results of these experiments, the scope of applicability conditions for this material and test modes necessary for parametric identification of models are selected. One fracture criterion is used that formally corresponds to the achievement of a threshold concentration of micro-damage in any volume of the material. Calculations of durability under conditions of varying temperature and variable loads are based on the relationship of plastic flow and failure processes distributed over the volume of the material. They are performed numerically over time steps depending on the ratio of the rate of change of temperature and stresses. Full article

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Alloys, Volume 2, Issue 3 (September 2023) – 7 articles

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