Metals

15 pages, 5777 KiB

Open AccessArticle

Processing Effects on the Formability of Magnesium Alloy Sheets

by Jan Bohlen^1,*, Guadalupe Cano¹, Daria Drozdenko², Patrik Dobron²

, Karl Ulrich Kainer¹, Sven Gall³, Sören Müller³ and Dietmar Letzig¹

¹ Magnesium Innovation Centre (MagIC), Helmholtz-Zentrum Geesthacht, Max-Planck Str. 1, D 21502 Geesthacht, Germany

² Department of Physics of Materials, Charles University, Ke Karlovu 5, CZ 121 16 Prague 2, Czech Republic

³ Extrusion Research & Development Center, TU Berlin, Gustav-Meyer-Allee 25, D 13355 Berlin, Germany

Metals 2018, 8(2), 147; https://doi.org/10.3390/met8020147 - 23 Feb 2018

Cited by 25 | Viewed by 5695

Abstract

As a generalized semi-finished product, the use of magnesium sheets requires addressing two major aspects of their processing: their microstructure and texture control, which are both essential for the forming behavior of such sheets during their forming to parts. Further, the processing of [...] Read more.

As a generalized semi-finished product, the use of magnesium sheets requires addressing two major aspects of their processing: their microstructure and texture control, which are both essential for the forming behavior of such sheets during their forming to parts. Further, the processing of such sheets is complex, and therefore expensive, and requires simplification. In this work, magnesium alloys AZ31, ZE10, and ME21 are investigated in the form of conventionally rolled sheets, as well as in the form of extruded sheets. Their microstructural and textural development are correlated to their mechanical and forming properties. During extrusion, strong textures develop that hinder stretch-forming operations, even in rare earth-containing alloys. Chemical composition and process parameters have a significant impact on the texture development, and enable the design of sheet materials with weak textures and potentially enhanced formability. Full article

(This article belongs to the Special Issue Latest Developments in Magnesium Technology—Alloying, Processing, Microstructure, Deformation Mechanism and Mechanical Properties)

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13 pages, 9237 KiB

Open AccessArticle

Numerical Simulation of Transient Multiphase Flow in a Five-Strand Bloom Tundish during Ladle Change

by Hua Zhang¹, Ronghua Luo², Qing Fang¹

, Hongwei Ni^1,* and Xiao Song¹

¹ The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, China

² Valin Xiangtan Iron and Steel Co., Ltd., Xiangtan 411101, China

Metals 2018, 8(2), 146; https://doi.org/10.3390/met8020146 - 23 Feb 2018

Cited by 22 | Viewed by 4385

Abstract

The steel-slag-air multiphase flow in a bloom tundish with five strands during the transient casting of the ladle change was simulated using the Volume of Fluid (VOF) model, and the formation mechanisms of macro-inclusions and the behavior of the steel-slag-air interface during the [...] Read more.

The steel-slag-air multiphase flow in a bloom tundish with five strands during the transient casting of the ladle change was simulated using the Volume of Fluid (VOF) model, and the formation mechanisms of macro-inclusions and the behavior of the steel-slag-air interface during the filling process were investigated. Water model experiments were conducted to validate the multiphase model. The results showed that the numerical results of slag entrapment behavior and the exposed area of steel are basically consistent with the experimental results. The flow of molten steel in the tundish is weak except for the region around the stopper rods at the end of the emptying process. Strong fluctuations in liquid level were formed during the filling process, showing two wave crests in front of and behind the shroud in the impact zone, which intensified with the increase in filling time and then declined gradually. Entrapment phenomena and exposure of liquid steel could not be observed before the filling stage. While the entrapped slag droplets mostly float up and can be removed within 40 s during the filling process, the remainder enters the casting zone through the baffle. The maximum exposed area of molten steel is 252 cm² when the filling time is 4.0 s. Full article

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10 pages, 5297 KiB

Open AccessArticle

An Investigation on the Adiabatic Shear Bands in Depleted U-0.75 wt % Ti Alloy under Dynamic Loading

by Bo Wang

, Yongxiang Dong^* and Guangyan Huang^*

State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing 100081, China

Metals 2018, 8(2), 145; https://doi.org/10.3390/met8020145 - 22 Feb 2018

Cited by 9 | Viewed by 7485

Abstract

Adiabatic shear bands in uranium alloy projectiles/penetrators, during penetration, allow them to “self-sharpen,” a process that is absent in most tungsten alloy projectiles/penetrators. U-0.75 wt % Ti alloy samples have been accelerated to impact steel targets, and the distribution of adiabatic shear bands [...] Read more.

Adiabatic shear bands in uranium alloy projectiles/penetrators, during penetration, allow them to “self-sharpen,” a process that is absent in most tungsten alloy projectiles/penetrators. U-0.75 wt % Ti alloy samples have been accelerated to impact steel targets, and the distribution of adiabatic shear bands in residual samples has been studied in detail to understand the effect of self-sharpening on penetration. In our study, self-sharpening was evidenced by the distribution of the shear bands in the recovered sample. The shear bands formed during impact were observed to change direction when they crossed grain boundaries, which indicated that the grain boundaries had an influence on the adiabatic shear bands of U-0.75 wt % Ti. Micro-hardness test results showed that the Vickers micro-hardness in the adiabatic shear zone was 18% lower than that in the matrix. In the split-Hopkinson pressure bar (SHPB) experiment, a strain rate of around 2891 s⁻¹ was the threshold strain rate that triggered the formation of adiabatic shear bands in the U-0.75 wt % Ti alloy. Full article

(This article belongs to the Special Issue Deformation Behavior of the Alloys under Simple and Combined Loading Conditions at Various Deformation Rate)

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10 pages, 5864 KiB

Open AccessArticle

Microstructure, Texture Evolution and Magnetic Properties of Fe-6.5 wt. % Si and Fe-6.5 wt. % Si-0.5 wt. % Cu Alloys during Rolling and Annealing Treatment

by Zhaoyang Cheng, Jing Liu^*, Jiachen Zhu, Zhidong Xiang, Juan Jia and Yunjie Bi

The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, China

Metals 2018, 8(2), 144; https://doi.org/10.3390/met8020144 - 22 Feb 2018

Cited by 4 | Viewed by 4404

Abstract

Sheets of Fe-6.5 wt. % Si and Fe-6.5 wt. % Si-0.5 wt. % Cu with the thickness of 0.3 mm have been produced by hot and warm rolling. The microstructure, texture evolution and magnetic properties of the two alloys were investigated. It was [...] Read more.

Sheets of Fe-6.5 wt. % Si and Fe-6.5 wt. % Si-0.5 wt. % Cu with the thickness of 0.3 mm have been produced by hot and warm rolling. The microstructure, texture evolution and magnetic properties of the two alloys were investigated. It was found that the addition of 0.5 wt. % Cu promoted the formation of shear bands during warm rolling, and enhanced the {110}<001> texture at surface layer and {111}<112> texture in the middle layer. After annealing treatment, a strong η fiber texture with a peak at {110}<001> was formed in the Fe-6.5 wt. % Si-0.5 wt. % Cu sample, while the Fe-6.5 wt. % Si sample was characterized by complex γ, η and λ fibers. The formation of dominating η fiber in the annealed Fe-6.5 wt. % Si-0.5 wt. % Cu sample is attributed to the shear bands formed in {111}<112> oriented grains. These shear bands in {111}<112> oriented grains acted as the nucleation sites of η oriented grains and promoted the growth of Goss oriented grains. The presence of strong η fiber with a peak at Goss in Fe-6.5 wt. % Si-0.5 wt. % Cu sample was the cause for the higher magnetic induction observed for this sample than for the Fe-6.5 wt. % Si sample. Full article

(This article belongs to the Special Issue Metallic Materials and Manufacturing)

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11 pages, 956 KiB

Open AccessArticle

Particle-Reinforced Aluminum Matrix Composites (AMCs)—Selected Results of an Integrated Technology, User, and Market Analysis and Forecast

by Anja Schmidt^1,*

, Steve Siebeck², Uwe Götze¹, Guntram Wagner²

and Daisy Nestler³

¹ Management Accounting and Control, Faculty of Economics and Business Administration, Chemnitz University of Technology, 09107 Chemnitz, Germany

² Composites and Material Compounds, Faculty of Mechanical Engineering, Chemnitz University of Technology, 09107 Chemnitz, Germany

³ Textile Plastic Composites and Hybrid Compounds, Faculty of Mechanical Engineering, Chemnitz University of Technology, 09107 Chemnitz, Germany

Metals 2018, 8(2), 143; https://doi.org/10.3390/met8020143 - 22 Feb 2018

Cited by 39 | Viewed by 5751

Abstract

The research and development of new materials such as particle-reinforced aluminum matrix composites (AMCs) will only result in a successful innovation if these materials show significant advantages not only from a technological, but also from an economic point of view. Against this background, [...] Read more.

The research and development of new materials such as particle-reinforced aluminum matrix composites (AMCs) will only result in a successful innovation if these materials show significant advantages not only from a technological, but also from an economic point of view. Against this background, in the Collaborative Research Center SFB 692, the concept of an integrated technology, user, and market analysis and forecast has been developed as a means for assessing the technological and commercial potential of new materials in early life cycle stages. After briefly describing this concept, it is applied to AMCs and the potential field of manufacturing aircraft components. Results show not only technological advances, but also considerable economic potential—the latter one primarily resulting from the possible weight reduction being enabled by the increased yield strength of the new material. Full article

(This article belongs to the Special Issue Scientific and Engineering Progress on Aluminum-Based Light-Weight Materials: Research Reports from the German Collaborative Research Center 692)

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10 pages, 6655 KiB

Open AccessArticle

The Properties of Arc-Sprayed Aluminum Coatings on Armor-Grade Steel

by Marcin Adamiak^1,*

, Artur Czupryński²

, Adam Kopyść¹, Zbigniew Monica³, Małgorzata Olender³ and Aleksander Gwiazda³

¹ Institute of Engineering Materials and Biomaterials, Faculty of Mechanical Engineering, Silesian University of Technology, Konarskiego 18a, 44-100 Gliwice, Poland

² Department of Welding, Faculty of Mechanical Engineering, Silesian University of Technology, Konarskiego 18a, 44-100 Gliwice, Poland

³ Institute of Computer Integrated Manufacturing, Faculty of Mechanical Engineering, Silesian University of Technology, Konarskiego 18a, 44-100 Gliwice, Poland

Metals 2018, 8(2), 142; https://doi.org/10.3390/met8020142 - 22 Feb 2018

Cited by 23 | Viewed by 7076

Abstract

This article presents the results of an examination of the properties of arc-sprayed aluminum on alloyed armor-grade steel. Thermal arc spraying was conducted with a EuTronic Arc Spray 4 wire arc sprayer. Aluminum wire 1.6 mm in diameter was used to produce dense, [...] Read more.

This article presents the results of an examination of the properties of arc-sprayed aluminum on alloyed armor-grade steel. Thermal arc spraying was conducted with a EuTronic Arc Spray 4 wire arc sprayer. Aluminum wire 1.6 mm in diameter was used to produce dense, abrasion- and erosion-resistant coatings approx. 1.0 mm thick with and without nickel/5% aluminum-buffered subcoating. Aluminum coatings were characterized in accordance with ASTM G 65-00 abrasion resistance test, ASTM G 76-95 erosion resistance tests, ASTM C 633-01 adhesion strength, HV0.1 hardness tests and metallographic analyses. Results demonstrate properties of arc-sprayed aluminum and aluminum-nickel material coatings that are especially promising in industrial applications where erosion-, abrasion- and corrosion-resistant coating properties are required. Full article

(This article belongs to the Special Issue Thermal Spray Processes: The Evolution of Equipment, Technology and Feedstock)

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11 pages, 5160 KiB

Open AccessArticle

The Formation and Evolution of Shear Bands in Plane Strain Compressed Nickel-Base Superalloy

by Bin Tang^1,*

, Lin Xiang¹

, Liang Cheng¹

, Degui Liu², Hongchao Kou¹ and Jinshan Li¹

¹ State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China

² AVIC Beijing Aeronautical Manufacturing Technology Research Institute, Beijing 100024, China

Metals 2018, 8(2), 141; https://doi.org/10.3390/met8020141 - 18 Feb 2018

Cited by 18 | Viewed by 5761

Abstract

The formation and evolution of shear bands in Inconel 718 nickel-base superalloy under plane strain compression was investigated in the present work. It is found that the propagation of shear bands under plane strain compression is more intense in comparison with conventional uniaxial [...] Read more.

The formation and evolution of shear bands in Inconel 718 nickel-base superalloy under plane strain compression was investigated in the present work. It is found that the propagation of shear bands under plane strain compression is more intense in comparison with conventional uniaxial compression. The morphology of shear bands was identified to generally fall into two categories: in “S” shape at severe conditions (low temperatures and high strain rates) and “X” shape at mild conditions (high temperatures and low strain rates). However, uniform deformation at the mesoscale without shear bands was also obtained by compressing at 1050 °C/0.001 s⁻¹. By using the finite element method (FEM), the formation mechanism of the shear bands in the present study was explored for the special deformation mode of plane strain compression. Furthermore, the effect of processing parameters, i.e., strain rate and temperature, on the morphology and evolution of shear bands was discussed following a phenomenological approach. The plane strain compression attempt in the present work yields important information for processing parameters optimization and failure prediction under plane strain loading conditions of the Inconel 718 superalloy. Full article

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15 pages, 4661 KiB

Open AccessArticle

Sensitivity Analysis of Oxide Scale Influence on General Carbon Steels during Hot Forging

by Bernd-Arno Behrens¹, Alexander Chugreev¹, Birgit Awiszus², Marcel Graf², Rudolf Kawalla³, Madlen Ullmann³, Grzegorz Korpala³

and Hendrik Wester^1,*

¹ Institute of Forming Technology and Machines, Leibniz Universität Hannover, 30823 Garbsen, Germany

² Professorship Virtual Production Engineering, Technische Universität Chemnitz, 09126 Chemnitz, Germany

³ Institute of Metal Forming, Technische Universität Freiberg, 09599 Freiberg, Germany

Metals 2018, 8(2), 140; https://doi.org/10.3390/met8020140 - 17 Feb 2018

Cited by 9 | Viewed by 4703

Abstract

Increasing product requirements have made numerical simulation into a vital tool for the time- and cost-efficient process design. In order to accurately model hot forging processes with finite, element-based numerical methods, reliable models are required, which take the material behaviour, surface phenomena of [...] Read more.

Increasing product requirements have made numerical simulation into a vital tool for the time- and cost-efficient process design. In order to accurately model hot forging processes with finite, element-based numerical methods, reliable models are required, which take the material behaviour, surface phenomena of die and workpiece, and machine kinematics into account. In hot forging processes, the surface properties are strongly affected by the growth of oxide scale, which influences the material flow, friction, and product quality of the finished component. The influence of different carbon contents on material behaviour is investigated by considering three different steel grades (C15, C45, and C60). For a general description of the material behaviour, an empirical approach is used to implement mathematical functions for expressing the relationship between flow stress and dominant influence variables like alloying elements, initial microstructure, and reheating mode. The deformation behaviour of oxide scale is separately modelled for each component with parameterized flow curves. The main focus of this work lies in the consideration of different materials as well as the calculation and assignment of their material properties in dependence on current process parameters by application of subroutines. The validated model is used to carry out the influence of various oxide scale parameters, like the scale thickness and the composition, on the hot forging process. Therefore, selected parameters have been varied within a numerical sensitivity analysis. The results show a strong influence of oxide scale on the friction behaviour as well as on the material flow during hot forging. Full article

(This article belongs to the Special Issue Advances in Plastic Forming of Metals)

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15 pages, 4327 KiB

Open AccessArticle

Effect of Nitric and Oxalic Acid Addition on Hard Anodizing of AlCu4Mg1 in Sulphuric Acid

by Maximilian Sieber¹, Roy Morgenstern^2,*, Ingolf Scharf² and Thomas Lampke²

¹ Lockwitzgrund 123a, D-01731 Kreischa, Germany

² Materials and Surface Engineering Group, Chemnitz University of Technology, D-09107 Chemnitz, Germany

Metals 2018, 8(2), 139; https://doi.org/10.3390/met8020139 - 17 Feb 2018

Cited by 15 | Viewed by 6356

Abstract

The anodic oxidation process is an established means for the improvement of the wear and corrosion resistance of high-strength aluminum alloys. For high-strength aluminum-copper alloys of the 2000 series, both the current efficiency of the anodic oxidation process and the hardness of the [...] Read more.

The anodic oxidation process is an established means for the improvement of the wear and corrosion resistance of high-strength aluminum alloys. For high-strength aluminum-copper alloys of the 2000 series, both the current efficiency of the anodic oxidation process and the hardness of the oxide coatings are significantly reduced in comparison to unalloyed substrates. With regard to this challenge, recent investigations have indicated a beneficial effect of nitric acid addition to the commonly used sulphuric acid electrolytes both in terms of coating properties and process efficiency. The present work investigates the anodic oxidation of the AlCu4Mg1 alloy in a sulphuric acid electrolyte with additions of nitric acid as well as oxalic acid as a reference in a full-factorial design of experiments (DOE). The effect of the electrolyte composition on process efficiency, coating thickness and hardness is established by using response functions. A mechanism for the participation of the nitric acid additive during the oxide formation is proposed. The statistical significance of the results is assessed by an analysis of variance (ANOVA). Eventually, scratch testing is applied in order to evaluate the failure mechanisms and the abrasion resistance of the obtained conversion coatings. Full article

(This article belongs to the Special Issue Scientific and Engineering Progress on Aluminum-Based Light-Weight Materials: Research Reports from the German Collaborative Research Center 692)

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12 pages, 8053 KiB

Open AccessArticle

The Effect of Interlayer Materials on the Joint Properties of Diffusion-Bonded Aluminium and Magnesium

by Stefan Habisch^1,*, Marcus Böhme²

, Siegfried Peter³, Thomas Grund² and Peter Mayr¹

¹ Institute of Joining and Assembly, Chemnitz University of Technology, D-09107 Chemnitz, Germany

² Institute of Materials Science and Engineering, Chemnitz University of Technology, D-09107 Chemnitz, Germany

³ Institute of Physics, Chemnitz University of Technology, D-09107 Chemnitz, Germany

Metals 2018, 8(2), 138; https://doi.org/10.3390/met8020138 - 17 Feb 2018

Cited by 19 | Viewed by 8132

Abstract

Diffusion bonding is a well-known technology for a wide range of advanced joining applications, due to the possibility of bonding different materials within a defined temperature-time-contact pressure regime in solid state. For this study, aluminium alloys AA 6060, AA 6082, AA 7020, AA [...] Read more.

Diffusion bonding is a well-known technology for a wide range of advanced joining applications, due to the possibility of bonding different materials within a defined temperature-time-contact pressure regime in solid state. For this study, aluminium alloys AA 6060, AA 6082, AA 7020, AA 7075 and magnesium alloy AZ 31 B are used to produce dissimilar metal joints. Titanium and silver were investigated as interlayer materials. SEM and EDXS-analysis, micro-hardness measurements and tensile testing were carried out to examine the influence of the interlayers on the diffusion zone microstructures and to characterize the joint properties. The results showed that the highest joint strength of 48 N/mm² was reached using an aluminium alloy of the 6000 series with a titanium interlayer. For both interlayer materials, intermetallic Al-Mg compounds were still formed, but the width and the level of hardness across the diffusion zone was significantly reduced compared to Al-Mg joints without interlayer. Full article

(This article belongs to the Special Issue Scientific and Engineering Progress on Aluminum-Based Light-Weight Materials: Research Reports from the German Collaborative Research Center 692)

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11 pages, 4404 KiB

Open AccessArticle

Effects of Pre-Strain on the Aging Behavior of Al 7075 Alloy for Hot-Stamping Capability

by Seon-Ho Jung^1,2,3, Jongsup Lee^2,* and Megumi Kawasaki^1,4,*

¹ Division of Materials Science and Engineering, Hanyang University, Seoul 04763, Korea

² Metal Forming Technology R&D Group, Korea Institute of Industrial Technology, Incheon 21999, Korea

³ Department of Mechanical Engineering, Inha University, Incheon 22212, Korea

⁴ School of Mechanical, Industrial & Manufacturing Engineering, Oregon State University, Corvallis, OR 97331, USA

Metals 2018, 8(2), 137; https://doi.org/10.3390/met8020137 - 16 Feb 2018

Cited by 22 | Viewed by 7514

Abstract

The present study investigates the significance of pre-strain on the T6 aging behavior of an Al 7075 alloy for evaluating the applicability of hot stamping. In practice, the alloy was pre-strained up to 15% during solution heat treatment at 480 °C prior to [...] Read more.

The present study investigates the significance of pre-strain on the T6 aging behavior of an Al 7075 alloy for evaluating the applicability of hot stamping. In practice, the alloy was pre-strained up to 15% during solution heat treatment at 480 °C prior to quenching, and artificial aging was conducted at 120 °C. The peak aging time and precipitation behavior were compared with the alloy with pre-straining at room temperature after quenching but immediately before the artificial aging. The results showed that increasing amounts of pre-strain tend to reduce the aging time up to 50% for achieving peak hardness, which is consistent with the alloy at the T6 condition. There is a limitation for the maximum attainable amount of pre-strain of 10% for the homogeneous distribution of strain when the alloy is strained at room temperature (RT) due to the low formability. The pre-strained alloy as hot stamping exhibited lowering of the peak reaction temperatures for dissolution and formation of Guinier–Preston (GP)-Zones and precipitated with increasing amounts of pre-strain towards 15% through the differential scanning calorimetry analysis, thereby confirming the shortening of the peak aging time. The present study confirms the excellent potential of the hot-stamping process to extend the capability of an Al 7075 alloy. Full article

(This article belongs to the Special Issue Heat Treatment of Aluminum Alloys)

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17 pages, 12911 KiB

Open AccessArticle

Finite Element Analysis of Surface Integrity in Deep Ball-Burnishing of a Biodegradable AZ31B Mg Alloy

by Mohammad Sharif Uddin^1,2,*

, Colin Hall²

, Ryan Hooper¹, Eric Charrault², Peter Murphy² and Vincent Santos¹

¹ School of Engineering, University of South Australia, Mawson Lakes, SA 5095, Australia

² Future Industries Institute, University of South Australia, Mawson Lakes, SA 5095, Australia

Metals 2018, 8(2), 136; https://doi.org/10.3390/met8020136 - 16 Feb 2018

Cited by 26 | Viewed by 5049

Abstract

As an effective and affordable technique, deep ball-burnishing has been applied to induce the plastic deformation of material, thus resulting in an increased surface hardness, compressive residual stress, and finish quality. Recent research shows that the fast degradation of an Mg alloy implant [...] Read more.

As an effective and affordable technique, deep ball-burnishing has been applied to induce the plastic deformation of material, thus resulting in an increased surface hardness, compressive residual stress, and finish quality. Recent research shows that the fast degradation of an Mg alloy implant is a prime limiting factor for its success in in vivo human trials. This paper presents a comprehensive investigation into deep ball-burnishing of a biodegradable AZ31B Mg alloy, in order to improve the alloy’s surface integrity. A series of experiments using an in-house built burnishing tool with a 10-mm steel ball have been conducted, with a key focus of exploring the influence of the major process parameters—e.g., burnishing force (750–2650 N), feed rate (150–500 mm/min), and step-over (0.05–0.15 mm)—on hardness and finish quality. With the aim of performing a parametric sensitivity study, a three-dimensional (3D) finite element (FE) model is developed to predict the deformation mechanics, plastic flow, hardness, and residual stress. The FE model agrees with the experiment, hence validating the reliability of the model. Results show that while burnishing significantly improves surface integrity compared to the untreated surface, burnishing force and step-over are shown to be dominant. The net material movement dictates generated residual stress (tensile or compressive), often negatively affecting the surface integrity (e.g., surface cracks), which may be responsible for the onset of corrosion. An appropriate burnishing strategy must therefore be planned, in order to achieve the intended process outcome. The resulting surface properties, enhanced by the deep ball-burnishing, are expected to potentially increase the corrosion resistance of AZ31B Mg alloy implants. Full article

(This article belongs to the Special Issue Advances in Enhancing Degradation Resistance of Metallic Implants by Surface Engineering)

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12 pages, 1865 KiB

Open AccessFeature PaperArticle

Chemical Synthesis and Characterization of Pd/SiO₂: The Effect of Chemical Reagent

by Aram L. Bugaev^*

, Vladimir A. Polyakov, Andrei A. Tereshchenko

, Ashura N. Isaeva, Alina A. Skorynina

, Elizaveta G. Kamyshova

, Andriy P. Budnyk, Tatiana A. Lastovina^* and Alexander V. Soldatov

The Smart Materials Research Center, Southern Federal University, 178/24 Sladkova, Rostov-on-Don 344090, Russia

Metals 2018, 8(2), 135; https://doi.org/10.3390/met8020135 - 16 Feb 2018

Cited by 13 | Viewed by 5639

Abstract

The size and shape distribution of metal nanoparticles (NPs) are important parameters that need to be tuned in order to achieve desired properties of materials for practical applications. In the current work, we present the synthesis of palladium NPs supported on silica by [...] Read more.

The size and shape distribution of metal nanoparticles (NPs) are important parameters that need to be tuned in order to achieve desired properties of materials for practical applications. In the current work, we present the synthesis of palladium NPs supported on silica by three different methods, applying reduction by sodium borohydride, hydrazine vapors, and polyethylene glycol (PEG). The synthesized materials were characterized by X-ray diffraction, X-ray fluorescence, transmission electron microscopy, surface area and porosity measurements, and thermogravimetric analysis. Similar nanoparticle sizes with narrow size distribution centered at 8 nm were obtained after reduction by sodium borohydride and hydrazine vapors, whereas the smallest particle size of about 4.8 nm was obtained after reduction by PEG. The effect of modification of the initial palladium chloride compound by ammonium hydroxide was found to lead to the formation of larger particles with average size of 15 nm and broader size distribution. In addition, the process of the reduction of palladium by PEG at different reduction stages was monitored by UV-Vis spectroscopy. CO-stripping voltammetry showed that reduction in hydrazine and in PEG allowed the preparation of Pd NPs with high electrochemically-active surface area. Such NPs are promising materials for electrocatalysis. Full article

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19 pages, 4681 KiB

Open AccessArticle

Comparative Effect of Mo and Cr on Microstructure and Mechanical Properties in NbV-Microalloyed Bainitic Steels

by Andrii Kostryzhev^1,*, Navjeet Singh¹, Liang Chen², Chris Killmore³ and Elena Pereloma^2,4

¹ Australian Steel Research Hub, University of Wollongong, Wollongong, NSW 2500, Australia

² School of Mechanical, Materials, Mechatronic and Biomedical Engineering, University of Wollongong, Wollongong, NSW 2500, Australia

³ BlueScope Steel Limited, Five Islands Road, Port Kembla, NSW 2505, Australia

⁴ UOW Electron Microscopy Centre, University of Wollongong, Wollongong, NSW 2519, Australia

Metals 2018, 8(2), 134; https://doi.org/10.3390/met8020134 - 16 Feb 2018

Cited by 33 | Viewed by 6171

Abstract

Steel product markets require the rolled stock with further increasing mechanical properties and simultaneously decreasing price. The steel cost can be reduced via decreasing the microalloying elements contents, although this decrease may undermine the mechanical properties. Multi-element microalloying with minor additions is the [...] Read more.

Steel product markets require the rolled stock with further increasing mechanical properties and simultaneously decreasing price. The steel cost can be reduced via decreasing the microalloying elements contents, although this decrease may undermine the mechanical properties. Multi-element microalloying with minor additions is the route to optimise steel composition and keep the properties high. However, this requires deep understanding of mutual effects of elements on each other’s performance with respect to the development of microstructure and mechanical properties. This knowledge is insufficient at the moment. In the present work we investigate the microstructure and mechanical properties of bainitic steels microalloyed with Cr, Mo, Nb and V. Comparison of 0.2 wt. % Mo and Cr additions has shown a more pronounced effect of Mo on precipitation than on phase balance. Superior strength of the MoNbV-steel originated from the strong solid solution strengthening effect. Superior ductility of the CrNbV-steel corresponded to the more pronounced precipitation in this steel. Nature of these mechanisms is discussed. Full article

(This article belongs to the Special Issue Advances in Microalloyed Steels)

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13 pages, 9264 KiB

Open AccessArticle

Elastic and Plastic Behavior of the QE22 Magnesium Alloy Reinforced with Short Saffil Fibers and SiC Particles

by Josef Zapletal^1,*, Zuzanka Trojanová²

, Pavel Doležal¹

, Stanislava Fintová³

and Michal Knapek²

¹ Institute of Materials Science and Engineering, Faculty of Mechanical Engineering, Brno University of Technology, Technická 2896/2, 616 69 Brno, Czech Republic

² Department of Physics of Materials, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, 121 16 Praha 2, Czech Republic

³ CEITEC IPM, Institute of Physics of Materials, Academy of Sciences of the Czech Republic, v. v. i., Žižkova 22, 616 62 Brno, Czech Republic

Metals 2018, 8(2), 133; https://doi.org/10.3390/met8020133 - 15 Feb 2018

Cited by 6 | Viewed by 5050

Abstract

Magnesium alloy QE22 (nominal composition 2 wt % Ag, 2 wt % mixture of rare earth elements, balance Mg) was reinforced with 5 vol % Saffil fibers and 15 vol % SiC particles. The hybrid composite was prepared via the squeeze cast technique. [...] Read more.

Magnesium alloy QE22 (nominal composition 2 wt % Ag, 2 wt % mixture of rare earth elements, balance Mg) was reinforced with 5 vol % Saffil fibers and 15 vol % SiC particles. The hybrid composite was prepared via the squeeze cast technique. The microstructure of the monolithic alloy and composite was analyzed using scanning electron microscopy. Elastic modulus was measured at room temperature and modeled by the Halpin–Tsai–Kardos mathematical model. The strengthening effect of fibers and particles was calculated and compared with the experimentally obtained values. The main strengthening terms were determined. Fracture surfaces were studied via scanning electron microscope. While the fracture of the matrix alloy had a mainly intercrystalline character, the failure of the hybrid composite was transcrystalline. Full article

(This article belongs to the Special Issue Metal Matrix Composites)

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15 pages, 5536 KiB

Open AccessArticle

Microstructure and Properties of Hybrid Laser Arc Welded Joints (Laser Beam-MAG) in Thermo-Mechanical Control Processed S700MC Steel

by Jacek Górka^1,*

and Sebastian Stano²

¹ Welding Department, Silesian University of Technology, Konarskiego 18A, 44-100 Gliwice, Poland

² Welding Institute in Gliwice, Bl. Czeslawa 16-18, 44-100 Gliwice, Poland

Metals 2018, 8(2), 132; https://doi.org/10.3390/met8020132 - 15 Feb 2018

Cited by 35 | Viewed by 7982

Abstract

The article presents the microstructure and properties of joints welded using the Hybrid Laser Arc Welding (HLAW) method laser beam-Metal Active Gas (MAG). The joints were made of 10-mm-thick steel S700MC subjected to the Thermo-Mechanical Control Process (TMCP) and characterised by a high [...] Read more.

The article presents the microstructure and properties of joints welded using the Hybrid Laser Arc Welding (HLAW) method laser beam-Metal Active Gas (MAG). The joints were made of 10-mm-thick steel S700MC subjected to the Thermo-Mechanical Control Process (TMCP) and characterised by a high yield point. In addition, the welding process involved the use of solid wire GMn4Ni1.5CrMo having a diameter of 1.2 mm. Non-destructive tests involving the joints made it possible to classify the joints as representing quality level B in accordance with the ISO 12932 standard. Destructive tests of the joints revealed that the joints were characterised by tensile strength similar to that of the base material. The hybrid welding (laser beam-MAG) of steel S700MC enabled the obtainment of good plastic properties of welded joints. In each area of the welded joints, the toughness values satisfied the criteria related to the minimum allowed toughness value. Tests involving the use of a transmission electron microscope and performed in the weld area revealed the decay of the precipitation hardening effect (i.e., the lack of precipitates having a size of several nm) and the presence of coagulated titanium-niobium precipitates having a size of 100 nm, restricting the growth of recrystallised austenite grains, as well as of spherical stable TiO precipitates (200 nm) responsible for the nucleation of ferrite inside austenite grains (significantly improving the plastic properties of joints). The tests demonstrated that it is possible to make welded joints satisfying quality-related requirements referred to in ISO 15614-14. Full article

(This article belongs to the Special Issue Laser Welding)

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16 pages, 11052 KiB

Open AccessArticle

Sliding Contact Wear Damage of EBM built Ti6Al4V: Influence of Process Induced Anisotropic Microstructure

by Jae Joong Ryu^1,*, Sanjay Shrestha¹, Guha Manogharan² and Jai K. Jung³

¹ Department of Mechanical, Industrial, and Manufacturing Engineering, Youngstown State University, Youngstown, OH 44555, USA

² Department of Mechanical and Nuclear Engineering, Pennsylvania State University, University Park, PA 16801, USA

³ Department of Civil/Environmental and Chemical Engineering, Youngstown State University, Youngstown, OH 44555, USA

Metals 2018, 8(2), 131; https://doi.org/10.3390/met8020131 - 13 Feb 2018

Cited by 16 | Viewed by 5010

Abstract

Process-induced directional microstructure is identified as one of the key factors of anisotropic mechanical properties. This directional property significantly affects surface contact fatigue and corrosion of electron beam melting (EBM) built biomedical implants. In the current study, material removal on EBM built titanium [...] Read more.

Process-induced directional microstructure is identified as one of the key factors of anisotropic mechanical properties. This directional property significantly affects surface contact fatigue and corrosion of electron beam melting (EBM) built biomedical implants. In the current study, material removal on EBM built titanium (Ti6Al4V) subjected to reciprocating motion of commercially pure titanium spherical slider is investigated to identify the influence of the process-induced layered structure and environments on wear damage. Specimens developed by two different build orientations are mechanically stimulated using different sliding directions with nominally elastic normal load in dry, passivating, and synovial environments. It was noticed that EBM orientation significantly changes wear behavior in ambient environment. Wear resistance of mill-annealed Ti6Al4V was improved in passivating environment. Implications to improve useful life of orthopedic implants are discussed. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Metallic Alloys Produced by Additive Manufacturing)

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12 pages, 6928 KiB

Open AccessArticle

Evaluation of Primary Water Stress Corrosion Cracking Resistance of Three Heats of Alloy 600 in 400 °C Hydrogenated Steam Condition

by Eunsub Yun^1,2, Hansub Chung¹ and Changheui Jang^2,*

¹ Central Research Institute, Korea Hydro and Nuclear Co., Ltd., 70, 1312-gil, Yuseong-daero, Yuseong-gu, Daejeon 34101, Korea

² Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Korea

Metals 2018, 8(2), 130; https://doi.org/10.3390/met8020130 - 12 Feb 2018

Cited by 2 | Viewed by 4396

Abstract

For Alloy 600, primary water stress corrosion cracking (PWSCC) is one of the key material degradation mechanisms in pressurized water reactors (PWRs). To identify the governing factors of PWSCC resistance, a systematic investigation into the role of each factor was performed. A PWSCC [...] Read more.

For Alloy 600, primary water stress corrosion cracking (PWSCC) is one of the key material degradation mechanisms in pressurized water reactors (PWRs). To identify the governing factors of PWSCC resistance, a systematic investigation into the role of each factor was performed. A PWSCC initiation test was performed for 3 heats of Alloy 600 in the 400 °C hydrogenated steam condition. Based on the test results, the effects of known factors like chemical composition, mechanical strength, grain boundary carbide coverage, grain boundary character, and surface cold work on PWSCC resistance were discussed. In addition, surface oxide morphology and penetrative oxide depth was compared. From this study, grain boundary character was considered to be the most dominant factor affecting the PWSCC resistance. Full article

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18 pages, 6756 KiB

Open AccessReview

Atomistic Simulations to Predict Favored Glass-Formation Composition and Ion-Beam-Mixing of Nano-Multiple-Metal-Layers to Produce Ternary Amorphous Films

by M. H. Yang, J. H. Li, B. X. Liu and J. B. Liu^*

Key Laboratory of Advanced Materials (MOE), School of Materials science and Engineering, Tsinghua University, Beijing 100084, China

Metals 2018, 8(2), 129; https://doi.org/10.3390/met8020129 - 11 Feb 2018

Cited by 2 | Viewed by 4729

Abstract

Based on the framework of long-range empirical formulas, the interatomic potentials were constructed for the Ni-Nb-Mo (fcc-bcc-bcc) and Ni-Zr-Mo (fcc-hcp-bcc) ternary metal systems. Applying the constructed potentials, atomistic simulations were performed [...] Read more.

Based on the framework of long-range empirical formulas, the interatomic potentials were constructed for the Ni-Nb-Mo (fcc-bcc-bcc) and Ni-Zr-Mo (fcc-hcp-bcc) ternary metal systems. Applying the constructed potentials, atomistic simulations were performed to predict the energetically favored glass formation regions (GFRs) in the respective composition triangles of the systems. In addition, the amorphization driving forces (ADFs), i.e., the energy differences between the solid solutions and disordered phases, were computed and appeared to correlate with the so-called glass forming abilities. To verify the atomistic prediction, ion beam mixing with nano-multiple-metal-layers was carried out to produce ternary amorphous films. The results showed that the composition of ternary amorphous films obtained by ion beam mixing all locate inside the GFRs, supporting the predictions of atomistic simulations. Interestingly, the minimum ion dosage required for amorphization showed a negative correlation with the calculated ADF, implying that the predicted amorphization driving force could be an indicator of the glass formation ability. Full article

(This article belongs to the Special Issue Metallic Films: From Nanofabrication and Nanostructuration to Characterizations and Applications)

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12 pages, 6074 KiB

Open AccessArticle

Finite Element Simulation of the Presta Joining Process for Assembled Camshafts: Application to Aluminum Shafts

by Robert Scherzer^1,*, Sebastian Fritsch², Ralf Landgraf¹

, Jörn Ihlemann¹ and Martin Franz-Xaver Wagner²

¹ Chair of Solid Mechanics, Institute of Mechanics and Thermodynamics, Chemnitz University of Technology, Reichenhainer Str. 70, D-09126 Chemnitz, Germany

² Chair of Materials Science, Institute of Materials Science and Engineering, Chemnitz University of Technology, Erfenschlager Str. 73, D-09125 Chemnitz, Germany

Metals 2018, 8(2), 128; https://doi.org/10.3390/met8020128 - 11 Feb 2018

Cited by 7 | Viewed by 4931

Abstract

This work shows a sequence of numerical models for the simulation of the Presta joining process: a well-established industrial process for manufacturing assembled camshafts. The operation is divided into two sub-steps: the rolling of the shaft to widen the cam seat and the [...] Read more.

This work shows a sequence of numerical models for the simulation of the Presta joining process: a well-established industrial process for manufacturing assembled camshafts. The operation is divided into two sub-steps: the rolling of the shaft to widen the cam seat and the joining of the cam onto the shaft. When manufactured, the connection is tested randomly by loading it with a static torque. Subsequently, there are three numerical models using the finite element method. Additionally, a material model of finite strain viscoplasticity with nonlinear kinematic hardening is used throughout the whole simulation process, which allows a realistic representation of the material behavior even for large deformations. In addition, it enables a transfer of the deformation history and of the internal stresses between different submodels. This work also shows the required parameter identification and the associated material tests. After comparing the numerical results with experimental studies of the manufacturing process for steel-steel connections, the models are used to extend the joining process to the utilization of aluminum shafts. Full article

(This article belongs to the Special Issue Scientific and Engineering Progress on Aluminum-Based Light-Weight Materials: Research Reports from the German Collaborative Research Center 692)

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2 pages, 140 KiB

Open AccessEditorial

Corrosion: Critical Challenge in Wider Use of Magnesium Alloys

by Raman Singh^1,*

, Vijayaraghavan Venkatesh^2,* and Vinod Kumar^3,4,*

¹ Departments of Mechanical & Aerospace Engineering and Chemical Engineering, Monash University, Melbourne, VIC 3800, Australia

² School of Mechanical and Manufacturing Engineering, The University of New South Wales, Sydney, NSW 2052, Australia

³ Department of Metallurgical and Materials Engineering, Malaviya National Institute of Technology, Jaipur 302017, India

⁴ Discipline of Metallurgy Engineering and Materials Science, Indian Institute of Technology Indore, Indore 453552, India

Metals 2018, 8(2), 127; https://doi.org/10.3390/met8020127 - 11 Feb 2018

Cited by 13 | Viewed by 3888

Abstract

Magnesium alloys, given their high strength-to-weight ratio, are very attractive materials for applications such as aerospace and automotive components.[...] Full article

(This article belongs to the Special Issue Corrosion of Magnesium Alloys)

12 pages, 3890 KiB

Open AccessArticle

Slurry Erosion Behavior of Al_xCoCrFeNiTi_0.5 High-Entropy Alloy Coatings Fabricated by Laser Cladding

by Jianhua Zhao^1,2, Aibin Ma^1,*, Xiulin Ji^2,*

, Jinghua Jiang¹ and Yayun Bao²

¹ College of Mechanics and Materials, Hohai University, Nanjing 210098, China

² College of Mechanical and Electrical Engineering, Hohai University, Changzhou 213022, China

Metals 2018, 8(2), 126; https://doi.org/10.3390/met8020126 - 11 Feb 2018

Cited by 35 | Viewed by 7004

Abstract

High-entropy alloys (HEAs) have gained extensive attention due to their excellent properties and the related scientific value in the last decade. In this work, Al_xCoCrFeNiTi_0.5 HEA coatings (x: molar ratio, x = 1.0, 1.5, 2.0, and 2.5) were [...] Read more.

High-entropy alloys (HEAs) have gained extensive attention due to their excellent properties and the related scientific value in the last decade. In this work, Al_xCoCrFeNiTi_0.5 HEA coatings (x: molar ratio, x = 1.0, 1.5, 2.0, and 2.5) were fabricated on Q345 steel substrate by laser-cladding process to develop a practical protection technology for fluid machines. The effect of Al content on their phase evolution, microstructure, and slurry erosion performance of the HEA coatings was studied. The Al_xCoCrFeNiTi_0.5 HEA coatings are composed of simple face-centered cubic (FCC), body-centered cubic (BCC) and their mixture phase. Slurry erosion tests were conducted on the HEA coatings with a constant velocity of 10.08 m/s and 16–40 meshs and particles at impingement angles of 15, 30, 45, 60 and 90 degrees. The effect of three parameters, namely impingement angle, sand concentration and erosion time, on the slurry erosion behavior of Al_xCoCrFeNiTi_0.5 HEA coatings was investigated. Experimental results show AlCoCrFeNiTi_0.5 HEA coating follows a ductile erosion mode and a mixed mode (neither ductile nor brittle) for Al_1.5CoCrFeNiTi_0.5 HEA coating, while Al_2.0CoCrFeNiTi_0.5 and Al_2.5CoCrFeNiTi_0.5 HEA coatings mainly exhibit brittle erosion mode. AlCoCrFeNiTi_0.5 HEA coating has good erosion resistance at all investigated impingement angles due to its high hardness, good plasticity, and low stacking fault energy (SFE). Full article

(This article belongs to the Special Issue Complex Concentrated Alloys (CCAs) - Current Understanding and Future Opportunities)

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5 pages, 159 KiB

Open AccessEditorial

Novel Research for Development of Shape Memory Alloys

by Takuo Sakon

Department of Mechanical and Systems Engineering, Faculty of Science and Technology, Ryukoku University, Otsu, Shiga 520-2194, Japan

Metals 2018, 8(2), 125; https://doi.org/10.3390/met8020125 - 11 Feb 2018

Cited by 5 | Viewed by 4004

Abstract

Shape memory alloys have attracted much attention due to their attractive properties for applications as well as their basic aspects of deformation and transformation in structural and magnetic behavior.[...] Full article

(This article belongs to the Special Issue Shape Memory Alloys 2017)

10 pages, 5785 KiB

Open AccessArticle

Effects of Zr Additive on Microstructure, Mechanical Properties, and Fractography of Al-Si Alloy

by Hui Qian, Degui Zhu^*, Chunfeng Hu and Xiaosong Jiang

Key Laboratory of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031, China

Metals 2018, 8(2), 124; https://doi.org/10.3390/met8020124 - 10 Feb 2018

Cited by 20 | Viewed by 5669

Abstract

The effects of Zr additive on the microstructure, mechanical properties, and fracture behavior of Al-Si alloy were systematically investigated. The additive of Zr obviously reduced the size of Si particles and changed its morphology. Grain size refinement was promoted by the reaction between [...] Read more.

The effects of Zr additive on the microstructure, mechanical properties, and fracture behavior of Al-Si alloy were systematically investigated. The additive of Zr obviously reduced the size of Si particles and changed its morphology. Grain size refinement was promoted by the reaction between Al and Zr forming Al₃Zr and ZrSi₂ compounds. Compared to a Zr-free alloy, the additive enhanced the tensile strength, compressive strength, shear strength, and hardness. The optimized Zr content was 2.4 wt % corresponding to a tensile strength of 231.1 MPa, compressive strength of 343.1 MPa, shear strength of 174.9 MPa, and hardness of 85.5 HV, greater than those of the Zr-free alloy. This illustrates that fine-grain strengthening and the existence of a second phase can improve the mechanical properties of Al-Si alloy. The fracture surface of Al-Si alloy without Zr additive showed a brittle fracture mode and there were no pits on the fractured surface. In the presence of Zr addictive, a typical plastic deformation with a large amount of pits was evidenced. Full article

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13 pages, 8322 KiB

Open AccessArticle

Evolution of Microstructure and Mechanical Properties of a CoCrFeMnNi High-Entropy Alloy during High-Pressure Torsion at Room and Cryogenic Temperatures

by Sergey Zherebtsov¹, Nikita Stepanov¹

, Yulia Ivanisenko², Dmitry Shaysultanov¹

, Nikita Yurchenko¹, Margarita Klimova^1,* and Gennady Salishchev¹

¹ Laboratory of Bulk Nanostructured Materials, Belgorod State University, 308015 Belgorod, Russia

² Karlsruhe Institute of Technology, Institute of Nanotechnology, 76021 Karlsruhe, Germany

Metals 2018, 8(2), 123; https://doi.org/10.3390/met8020123 - 10 Feb 2018

Cited by 45 | Viewed by 7281

Abstract

High-pressure torsion (HPT) is applied to a face-centered cubic CoCrFeMnNi high-entropy alloy at 293 and 77 K. Processing by HPT at 293 K produced a nanostructure consisted of (sub)grains of ~50 nm after a rotation for 180°. The microstructure evolution is associated with [...] Read more.

High-pressure torsion (HPT) is applied to a face-centered cubic CoCrFeMnNi high-entropy alloy at 293 and 77 K. Processing by HPT at 293 K produced a nanostructure consisted of (sub)grains of ~50 nm after a rotation for 180°. The microstructure evolution is associated with intensive deformation-induced twinning, and substructure development resulted in a gradual microstructure refinement. Deformation at 77 K produces non-uniform structure composed of twinned and fragmented areas with higher dislocation density then after deformation at room temperature. The yield strength of the alloy increases with the angle of rotation at HPT at room temperature at the cost of reduced ductility. Cryogenic deformation results in higher strength in comparison with the room temperature HPT. The contribution of Hall–Petch hardening and substructure hardening in the strength of the alloy in different conditions is discussed. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Structural Metals and Alloys)

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12 pages, 5128 KiB

Open AccessArticle

Strain Hardening Behavior and Microstructure Evolution of High-Manganese Steel Subjected to Interrupted Tensile Tests

by Adam Grajcar^*

, Aleksandra Kozłowska

and Barbara Grzegorczyk

Faculty of Mechanical Engineering, Silesian University of Technology, 18a Konarskiego Street, 44-100 Gliwice, Poland

Metals 2018, 8(2), 122; https://doi.org/10.3390/met8020122 - 10 Feb 2018

Cited by 13 | Viewed by 6065

Abstract

Strain hardening behavior and the corresponding microstructure evolution of the high-manganese steel with additions of Si and Al were investigated in this study. Thermomechanically processed and solution-heat-treated sheet steels were compared under conditions of interrupted tensile tests. Relationships between microstructure and strain hardening [...] Read more.

Strain hardening behavior and the corresponding microstructure evolution of the high-manganese steel with additions of Si and Al were investigated in this study. Thermomechanically processed and solution-heat-treated sheet steels were compared under conditions of interrupted tensile tests. Relationships between microstructure and strain hardening were assessed for different strain levels using light microscopy and scanning electron microscopy techniques. It was found that the deformation of both steels at low strain levels was dominated by dislocation glide before the occurrence of mechanical twinning. The amount of twins, slip lines, and bands was increasing gradually up to the point of necking. As the strain level increased, dislocation density within twinning areas becomes higher, which enhances the strength, the work hardening exponent, and the work hardening rate of the investigated high-manganese sheet steels. Full article

(This article belongs to the Special Issue Physical Metallurgy of High Performance Steels)

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10 pages, 4016 KiB

Open AccessFeature PaperArticle

Exothermic Reaction Kinetics in High Energy Density Al-Ni with Nanoscale Multilayers Synthesized by Cryomilling

by Minseok Oh¹, Min Chul Oh¹, Deokhyun Han^1,2, Sang-Hyun Jung³ and Byungmin Ahn^1,4,*

¹ Department of Energy Systems Research, Ajou University, Suwon 16499, Korea

² Advanced Materials & Processing Center, Institute for Advanced Engineering, Yongin 17180, Korea

³ The 4th Research and Development, Agency for Defense Development, Daejeon 34060, Korea

⁴ Department of Materials Science and Engineering, Ajou University, Suwon 16499, Korea

Metals 2018, 8(2), 121; https://doi.org/10.3390/met8020121 - 9 Feb 2018

Cited by 7 | Viewed by 5580

Abstract

The Al-Ni system is known as a high energy density materials (HEDM) because of its highly exothermic nature during intermetallic compound (IMC) formation. In this study, elemental Al and Ni powder were milled to explore the effect of cryomilling atmosphere on the microstructure [...] Read more.

The Al-Ni system is known as a high energy density materials (HEDM) because of its highly exothermic nature during intermetallic compound (IMC) formation. In this study, elemental Al and Ni powder were milled to explore the effect of cryomilling atmosphere on the microstructure and exothermic behavior. Scanning electron microscope (SEM) observations show continuous structural refinement up to 8 h of cryomilling. No IMC phase was detected in the X-ray diffraction (XRD) spectrum. Differential thermal analyzer (DTA) results show two exothermic peaks for 8 h cryomilled powder as compared to that of powder milled for 1 h. The ignition temperature of prepared powder mixture also decreased due to gradual structural refinement. The activation energy was also calculated and correlated with the DTA and SEM results. The cryomilled Al-Ni powder is composed of fine Al-Ni metastable junctions which improve the reactivity at a lower exothermic reaction temperature. Full article

(This article belongs to the Special Issue Synthesis and Properties of Bulk Nanostructured Metallic Materials)

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3 pages, 148 KiB

Open AccessEditorial

Recent Advances in Study of Solid-Liquid Interfaces and Solidification of Metals

by Mohsen Asle Zaeem

Department of Materials Science and Engineering, Missouri University of Science and Technology, Rolla, MO 65401, USA

Metals 2018, 8(2), 120; https://doi.org/10.3390/met8020120 - 9 Feb 2018

Cited by 1 | Viewed by 3516

Abstract

Solidification occurs in several material processing methods, such as in casting, welding, and laser additive manufacturing of metals, and it controls the nano- and microstructures, as well as the overall properties of the products[...] Full article

(This article belongs to the Special Issue Recent Advances in Study of Solid-Liquid Interfaces and Solidification of Metals)

15 pages, 8597 KiB

Open AccessArticle

Characteristics of Metal Magnetic Memory Testing of 35CrMo Steel during Fatigue Loading

by Zhibin Hu¹, Jianchun Fan^1,*, Shengnan Wu¹, Haoyuan Dai¹ and Shujie Liu²

¹ College of Mechanical and Transportation Engineering, China University of Petroleum-Beijing, Beijing 102200, China

² China National Offshore Oil Corporation, Beijing 100029, China

Metals 2018, 8(2), 119; https://doi.org/10.3390/met8020119 - 8 Feb 2018

Cited by 27 | Viewed by 5620

Abstract

The fatigue fracture of a drillstring could cause drilling disturbances and some negative impacts (e.g., economic loss) will be brought when restoring the drillstring to functionality. In order to evaluate the effects of the fatigue damage of the drillstring during drilling, a new [...] Read more.

The fatigue fracture of a drillstring could cause drilling disturbances and some negative impacts (e.g., economic loss) will be brought when restoring the drillstring to functionality. In order to evaluate the effects of the fatigue damage of the drillstring during drilling, a new apparatus, which could monitor the load level in real-time, was built to perform the four-point bending fatigue test on 35CrMo steel, a typical material of drillstrings. Such an apparatus is based on metal magnetic memory (MMM) technology and can acquire the tangential and normal components of MMM signals. Based on the analysis of the change of surface morphology and MMM signals, it was concluded that the variation of MMM signals could be divided into four stages, which are used to accurately describe the fatigue damage process of the drillstring. Additionally, the MMM signal characteristics are introduced to especially evaluate the fatigue damage of the drillstring, including crack initiation. Furthermore, the scanning electron microscopy (SEM) results demonstrated that morphologies of fatigue fracture were related to the variation of MMM signals. Linear fitting results indicated that fatigue crack length had a good linear relationship with the characteristics, so it is feasible to monitor fatigue damage and predict the residual life of a drillstring by using MMM technology. Full article

(This article belongs to the Special Issue Advanced Non-Destructive Testing in Steels)

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12 pages, 14527 KiB

Open AccessArticle

Enhanced Compressive Property of Al Composite Foams at Elevated Temperatures via Plasma Electrolytic Oxidation

by Huamin Liu^1,2, Wenchi Pan², Fujian Si², Kuo Huang³, Yan Liu⁴ and Jiaan Liu^2,*

¹ Roll Forging Research Institute, Jilin University, Changchun 130022, China

² Key Laboratory of Automobile Materials (Ministry of Education), College of Materials Science and Engineering, Jilin University, Changchun 130022, China

³ Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, UK

⁴ Key Laboratory of Bionic Engineering (Ministry of Education), Jilin University, Changchun 130022, China

Metals 2018, 8(2), 118; https://doi.org/10.3390/met8020118 - 8 Feb 2018

Cited by 9 | Viewed by 3819

Abstract

The present work investigates the compressive property of Al matrix composite foams at different temperatures between room temperature and 200 °C. Elevated temperature results in a decreased compressive strength and energy absorption capacity of as-received Al foams. Therefore, to maintain the compressive property, [...] Read more.

The present work investigates the compressive property of Al matrix composite foams at different temperatures between room temperature and 200 °C. Elevated temperature results in a decreased compressive strength and energy absorption capacity of as-received Al foams. Therefore, to maintain the compressive property, the Al₂O₃ ceramic coating was deposited on the Al struts of the foams by the plasma electrolytic oxidation (PEO) process to form Al₂O₃/Al composite foams. As a consequence, the composite foams exhibit a higher compressive strength and energy absorption capacity as compared with the as-received Al foams at both room temperature and elevated temperatures because of the reinforced effect of the Al₂O₃ ceramic on the foam strut. The related mechanisms were explained by fractography, microstructure observation and phase composition analysis using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). Full article

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