Metals

1346 KiB

Open AccessArticle

Predicted Fracture Behavior of Shaft Steels with Improved Corrosion Resistance

by Goran Vukelic and Josip Brnic

Metals 2016, 6(2), 40; https://doi.org/10.3390/met6020040 - 19 Feb 2016

Cited by 13 | Viewed by 4675

One of the crucial steps in the shaft design process is the optimal selection of the material. Two types of shaft steels with improved corrosion resistances, 1.4305 and 1.7225, were investigated experimentally and numerically in this paper in order to determine some of [...] Read more.

One of the crucial steps in the shaft design process is the optimal selection of the material. Two types of shaft steels with improved corrosion resistances, 1.4305 and 1.7225, were investigated experimentally and numerically in this paper in order to determine some of the material characteristics important for material selection in the engineering design process. Ultimate tensile strength and yield strength have been experimentally obtained, proving that steel 1.4305 has higher values of both. In addition, J-integral is numerically determined as a measure of crack driving force for finite element models of standardized fracture specimens (single-edge notched bend and disc compact tension). Obtained J values are plotted versus specimen crack growth size (Δa) for different specimen geometries (a/W). Higher resulting values of J-integral for steel 1.4305 as opposed to 1.7225 can be noted. Results can be useful as a fracture parameter in fracture toughness assessment, although this procedure differs from experimental analysis. Full article

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2110 KiB

Open AccessArticle

Effect of Sb Addition on the Solidification of Deeply Undercooled Ag-28.1 wt. % Cu Eutectic Alloy

by Su Zhao, Yunxia Chen and Donglai Wei

Metals 2016, 6(2), 39; https://doi.org/10.3390/met6020039 - 17 Feb 2016

Cited by 1 | Viewed by 4470

Abstract

Ag-28.1 wt. % Cu eutectic alloy solidifies in the form of eutectic dendrite at undercooling above 76 K. The remelting and ripening of the original lamellar eutectics result in the formation of the anomalous eutectics in the final microstructure. The addition of the [...] Read more.

Ag-28.1 wt. % Cu eutectic alloy solidifies in the form of eutectic dendrite at undercooling above 76 K. The remelting and ripening of the original lamellar eutectics result in the formation of the anomalous eutectics in the final microstructure. The addition of the third element Sb (0.5 and 1 wt. %) does not change the growth mode, but enlarges the volume fraction of anomalous eutectics because of the increasing recalescence rate. The additional constitutional supercooling owing to the Sb enrichment ahead of the eutectic interface promotes the branching of the interface and as a result fine lamellar eutectic arms form around the anomalous eutectics in the Sb-added Ag-28.1 wt. % Cu eutectic alloy. Full article

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3277 KiB

Open AccessArticle

Effect of Al Hot-Dipping on High-Temperature Corrosion of Carbon Steel in N₂/0.1% H₂S Gas

by Muhammad Ali Abro and Dong Bok Lee

Metals 2016, 6(2), 38; https://doi.org/10.3390/met6020038 - 17 Feb 2016

Cited by 6 | Viewed by 6043

Abstract

High-temperature corrosion of carbon steel in N₂/0.1% H₂S mixed gas at 600–800 °C for 50–100 h was studied after hot-dipping in the aluminum molten bath. Hot-dipping resulted in the formation of the Al topcoat and the Al-Fe alloy layer [...] Read more.

High-temperature corrosion of carbon steel in N₂/0.1% H₂S mixed gas at 600–800 °C for 50–100 h was studied after hot-dipping in the aluminum molten bath. Hot-dipping resulted in the formation of the Al topcoat and the Al-Fe alloy layer firmly adhered on the substrate. The Al-Fe alloy layer consisted primarily of a wide, tongue-like Al₅Fe₂ layer and narrow Al₃Fe layer. When corroded at 800 °C for 100 h, the Al topcoat partially oxidized to the protective but non-adherent α-Al₂O₃ layer, and the interdiffusion converted the Al-Fe alloy layer to an (Al₁₃Fe₄, AlFe₃)-mixed layer. The interdiffusion also lowered the microhardness of the hot-dipped steel. The α-Al₂O₃ layer formed on the hot-dipped steel protected the carbon steel against corrosion. Without the Al hot-dipping, the carbon steel failed by forming a thick, fragile, and non-protective FeS scale. Full article

(This article belongs to the Special Issue Oxidation of Metals)

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3756 KiB

Open AccessArticle

Formation and Dissolution of γ’ Precipitates in IN792 Superalloy at Elevated Temperatures

by Pavel Strunz, Martin Petrenec, Jaroslav Polák, Urs Gasser and Gergely Farkas

Metals 2016, 6(2), 37; https://doi.org/10.3390/met6020037 - 17 Feb 2016

Cited by 8 | Viewed by 5650

Abstract

Precipitation of γ’ phase in nickel-base superalloy IN792-5A was studied using in-situ Small Angle Neutron Scattering (SANS). It was found that additional precipitates are formed after reheating above 600 °C when the material is previously fast cooled (100 K/min) from 900 °C. The [...] Read more.

Precipitation of γ’ phase in nickel-base superalloy IN792-5A was studied using in-situ Small Angle Neutron Scattering (SANS). It was found that additional precipitates are formed after reheating above 600 °C when the material is previously fast cooled (100 K/min) from 900 °C. The size distribution and volume fraction of the additional γ’ precipitates as well as of the already present medium-size precipitates in dependence on temperature were evaluated. The small precipitates can influence mechanical properties of the alloy, which exhibits an anomaly in the temperature dependence of the yield stress. Volume fraction of all precipitate populations above 900 °C was estimated as well. Full article

(This article belongs to the Special Issue Superalloys)

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3689 KiB

Open AccessArticle

Influence of the Hardfacing Welds Structure on Their Wear Resistance

by Janette Brezinová, Dagmar Draganovská, Anna Guzanová, Peter Balog and Ján Viňáš

Metals 2016, 6(2), 36; https://doi.org/10.3390/met6020036 - 17 Feb 2016

Cited by 22 | Viewed by 4873

Abstract

The contribution presents the research results of hardfacing metals’ resistance in conditions of abrasive wear. Two types of hardfacing electrodes with a different chemical composition were used in the creation of three layers of hardfacing metals. The chemical composition of electrodes determines the [...] Read more.

The contribution presents the research results of hardfacing metals’ resistance in conditions of abrasive wear. Two types of hardfacing electrodes with a different chemical composition were used in the creation of three layers of hardfacing metals. The chemical composition of electrodes determines the difference in a hardface deposit structure. We have investigated the influence of mixing the base metal and a filler metal and the influence of hardfacing welds structure on the resistance against abrasive wear. The results of the experiments have showed that the intensity of wear is very dependent on the parameters of wear as well as the morphology structure of hardfacing metals. Full article

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5266 KiB

Open AccessArticle

Microstructures and Mechanical Properties of Austempering SUS440 Steel Thin Plates

by Cheng-Yi Chen, Fei-Yi Hung, Truan-Sheng Lui and Li-Hui Chen

Metals 2016, 6(2), 35; https://doi.org/10.3390/met6020035 - 15 Feb 2016

Cited by 8 | Viewed by 7354

Abstract

SUS440 is a high-carbon stainless steel, and its martensite matrix has high heat resistance, high corrosion resistance, and high pressure resistance. It has been widely used in mechanical parts and critical materials. However, the SUS440 martempered matrix has reliability problems in thin plate [...] Read more.

SUS440 is a high-carbon stainless steel, and its martensite matrix has high heat resistance, high corrosion resistance, and high pressure resistance. It has been widely used in mechanical parts and critical materials. However, the SUS440 martempered matrix has reliability problems in thin plate applications and thus research uses different austempering heat treatments (tempering temperature: 200 °C–400 °C) to obtain a matrix containing bainite, retained austenite, martensite, and the M7C3 phase to investigate the relationships between the resulting microstructure and tensile mechanical properties. Experimental data showed that the austempering conditions of the specimen affected the volume fraction of phases and distribution of carbides. After austenitizing heat treatment (1080 °C for 30 min), the austempering of the SUS440 thin plates was carried out at a salt-bath temperature 300 °C for 120 min and water quenching was then used to obtain the bainite matrix with fine carbides, with the resulting material having a higher tensile fracture strength and average hardness (HRA 76) makes it suitable for use as a high-strength thin plate for industrial applications. Full article

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1887 KiB

Open AccessArticle

Wear Behaviour of A356/TiAl₃ in Situ Composites Produced by Mechanical Alloying

by Seda Çam, Vedat Demir and Dursun Özyürek

Metals 2016, 6(2), 34; https://doi.org/10.3390/met6020034 - 05 Feb 2016

Cited by 14 | Viewed by 4193

Abstract

In this study, the effects of in situ TiAl₃ particles on dry sliding wear behavior of A356 aluminum alloy (added Ti) composites were investigated. The wear samples were prepared by adding different amounts of Ti (4%, 6%, and 8%) into A356 powder [...] Read more.

In this study, the effects of in situ TiAl₃ particles on dry sliding wear behavior of A356 aluminum alloy (added Ti) composites were investigated. The wear samples were prepared by adding different amounts of Ti (4%, 6%, and 8%) into A356 powder alloy by mechanical alloying. The mechanically alloyed powders were cold pressed at 600 MPa and sintered 530 °C for 1 h in argon atmosphere and cooled in the furnace. After the sintering process, the samples were characterized. The results show that AlTi and TiAl₃ intermetallic phases were formed and their amount increased depending on the amount of Ti added into A356 powder alloy. Out of the samples sintered with different titanium amounts (1 h at 530 °C), the highest hardness value and, accordingly, the lowest wear amount, were observed in the alloy containing 8% Ti. Full article

(This article belongs to the Special Issue Powder Metallurgy)

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2172 KiB

Open AccessFeature PaperArticle

Monte Carlo Modelling of Single-Crystal Diffuse Scattering from Intermetallics

by Darren J. Goossens

Metals 2016, 6(2), 33; https://doi.org/10.3390/met6020033 - 04 Feb 2016

Cited by 2 | Viewed by 5138

Abstract

Single-crystal diffuse scattering (SCDS) reveals detailed structural insights into materials. In particular, it is sensitive to two-body correlations, whereas traditional Bragg peak-based methods are sensitive to single-body correlations. This means that diffuse scattering is sensitive to ordering that persists for just a few [...] Read more.

Single-crystal diffuse scattering (SCDS) reveals detailed structural insights into materials. In particular, it is sensitive to two-body correlations, whereas traditional Bragg peak-based methods are sensitive to single-body correlations. This means that diffuse scattering is sensitive to ordering that persists for just a few unit cells: nanoscale order, sometimes referred to as “local structure”, which is often crucial for understanding a material and its function. Metals and alloys were early candidates for SCDS studies because of the availability of large single crystals. While great progress has been made in areas like ab initio modelling and molecular dynamics, a place remains for Monte Carlo modelling of model crystals because of its ability to model very large systems; important when correlations are relatively long (though still finite) in range. This paper briefly outlines, and gives examples of, some Monte Carlo methods appropriate for the modelling of SCDS from metallic compounds, and considers data collection as well as analysis. Even if the interest in the material is driven primarily by magnetism or transport behaviour, an understanding of the local structure can underpin such studies and give an indication of nanoscale inhomogeneity. Full article

(This article belongs to the Special Issue Metals Challenged by Neutron and Synchrotron Radiation)

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3088 KiB

Open AccessArticle

Microstructure and High Temperature Deformation of Extruded Al-12Si-3Cu-Based Alloy

by Seung-Baek Yu and Mok-Soon Kim

Metals 2016, 6(2), 32; https://doi.org/10.3390/met6020032 - 02 Feb 2016

Cited by 7 | Viewed by 3932

Abstract

The high temperature deformation behavior of commercial Al-12Si-3Cu-2Ni-1Mg alloy (DM104™) which was fabricated by casting and subsequent hot extrusion was evaluated by compressive tests over the temperature range of 250–470 °C and strain rate range of 0.001–1/s. The extruded alloy had equiaxed grains, [...] Read more.

The high temperature deformation behavior of commercial Al-12Si-3Cu-2Ni-1Mg alloy (DM104™) which was fabricated by casting and subsequent hot extrusion was evaluated by compressive tests over the temperature range of 250–470 °C and strain rate range of 0.001–1/s. The extruded alloy had equiaxed grains, spherical Si particles and fine intermetallic phases, such as δ(Al₃NiCu) and Q(Al₅Cu₂Mg₃Si₆). The true stress-true strain curves from the compressive tests exhibited steady-state flow after reaching the peak stress. A close relationship between the steady-state stress and a constitutive equation for high temperature deformation was observed. Fine equiaxed grains and a dislocation structure within the equiaxed grains were observed in the deformed specimens, suggesting the occurrence of dynamic recrystallization during high temperature deformation. Full article

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3400 KiB

Open AccessFeature PaperArticle

Ti/Al Multi-Layered Sheets: Differential Speed Rolling (Part B)

by Jan Romberg, Jens Freudenberger, Hiroyuki Watanabe, Juliane Scharnweber, Andy Eschke, Uta Kühn, Hansjörg Klauß, Carl-Georg Oertel, Werner Skrotzki, Jürgen Eckert and Ludwig Schultz

Metals 2016, 6(2), 31; https://doi.org/10.3390/met6020031 - 02 Feb 2016

Cited by 8 | Viewed by 5381

Abstract

Differential speed rolling has been applied to multi-layered Ti/Al composite sheets, obtained from accumulative roll bonding with intermediate heat treatments being applied. In comparison to conventional rolling, differential speed rolling is more efficient in strengthening the composite due to the more pronounced grain [...] Read more.

Differential speed rolling has been applied to multi-layered Ti/Al composite sheets, obtained from accumulative roll bonding with intermediate heat treatments being applied. In comparison to conventional rolling, differential speed rolling is more efficient in strengthening the composite due to the more pronounced grain refinement. Severe plastic deformation by means of rolling becomes feasible if the evolution of common rolling textures in the Ti layers is retarded. In this condition, a maximum strength level of the composites is achieved, i.e., an ultimate tensile strength of 464 MPa, while the strain to failure amounts to 6.8%. The deformation has been observed for multi-layered composites. In combination with the analysis of the microstructure, this has been correlated to the mechanical properties. Full article

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9627 KiB

Open AccessFeature PaperArticle

Ti/Al Multi-Layered Sheets: Accumulative Roll Bonding (Part A)

by Jan Romberg, Jens Freudenberger, Hansjörg Bauder, Georg Plattner, Hans Krug, Frank Holländer, Juliane Scharnweber, Andy Eschke, Uta Kühn, Hansjörg Klauß, Carl-Georg Oertel, Werner Skrotzki, Jürgen Eckert and Ludwig Schultz

Metals 2016, 6(2), 30; https://doi.org/10.3390/met6020030 - 02 Feb 2016

Cited by 20 | Viewed by 6433

Abstract

Co-deformation of Al and Ti by accumulative roll bonding (ARB) with intermediate heat treatments is utilized to prepare multi-layered Ti/Al sheets. These sheets show a high specific strength due to the activation of various hardening mechanisms imposed during deformation, such as: hardening by [...] Read more.

Co-deformation of Al and Ti by accumulative roll bonding (ARB) with intermediate heat treatments is utilized to prepare multi-layered Ti/Al sheets. These sheets show a high specific strength due to the activation of various hardening mechanisms imposed during deformation, such as: hardening by grain refinement, work hardening and phase boundary hardening. The latter is even enhanced by the confinement of the layers during deformation. The evolution of the microstructure with a special focus on grain refinement and structural integrity is traced, and the correlation to the mechanical properties is shown. Full article

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2833 KiB

Open AccessArticle

Influences of Restaurant Waste Fats and Oils (RWFO) from Grease Trap as Binder on Rheological and Solvent Extraction Behavior in SS316L Metal Injection Molding

by Mohd Halim Irwan Ibrahim, Azriszul Mohd Amin, Rosli Asmawi and Najwa Mustafa

Metals 2016, 6(2), 19; https://doi.org/10.3390/met6020019 - 02 Feb 2016

Cited by 6 | Viewed by 5395

Abstract

This article deals with rheological and solvent extraction behavior of stainless steel 316L feedstocks using Restaurant Waste Fats and Oils (RWFO) from grease traps as binder components along with Polypropylene (PP) copolymer as a backbone binder. Optimal binder formulation and effect of solvent [...] Read more.

This article deals with rheological and solvent extraction behavior of stainless steel 316L feedstocks using Restaurant Waste Fats and Oils (RWFO) from grease traps as binder components along with Polypropylene (PP) copolymer as a backbone binder. Optimal binder formulation and effect of solvent extraction variables on green compacts are being analyzed. Four binder formulations based on volumetric ratio/weight fraction between PP and RWFO being mixed with 60% volumetric powder loading of SS316L powder each as feedstock. The rheological analysis are based on viscosity, shear rate, temperature, activation energy, flow behavior index, and moldability index. The optimal feedstock formulation will be injected to form green compact to undergo the solvent extraction process. Solvent extraction variables are based on solvent temperature which are 40 °C, 50 °C, and 60 °C with different organic solvents of n-hexane and n-heptane. Analysis of the weight loss percentage and diffusion coefficient is done on the green compact during the solvent extraction process. Differential Scanning Calorimeter (DSC) is used to confirm the extraction of the RWFO in green compacts. It is found that all binder fractions exhibit pseudoplastic behavior or shear thinning where the viscosity decreases with increasing shear rate. After considering the factors that affect the rheological characteristic of the binder formulation, feedstock with binder formulation of 20/20 volumetric ratio between PP and RWFO rise as the optimal binder. It is found that the n-hexane solvent requires less time for extracting the RWFO at the temperature of 60 °C as proved by its diffusion coefficient. Full article

(This article belongs to the Special Issue Metal Injection Moulding)

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1227 KiB

Open AccessArticle

Effect of Laser Surface Treatment on the Corrosion Behavior of FeCrAl-Coated TZM Alloy

by Jeong-Min Kim, Tae-Hyung Ha, Joon-Sik Park and Hyun-Gil Kim

Metals 2016, 6(2), 29; https://doi.org/10.3390/met6020029 - 29 Jan 2016

Cited by 11 | Viewed by 4812

Abstract

The current study involves the coating of Titanium-Zirconium-Molybdenum (TZM) alloy with FeCrAl through plasma thermal spraying which proved effective in improving the oxidation resistance of the substrate. A post-laser surface melting treatment further enhanced the surface protection of the TZM alloy. Oxidation tests [...] Read more.

The current study involves the coating of Titanium-Zirconium-Molybdenum (TZM) alloy with FeCrAl through plasma thermal spraying which proved effective in improving the oxidation resistance of the substrate. A post-laser surface melting treatment further enhanced the surface protection of the TZM alloy. Oxidation tests conducted at 1100 °C in air indicated that some Mo oxides were formed at the surface but a relatively small amount of weight reduction was observed for FeCrAl-coated TZM alloys up to 60 min of treatment. The post-laser surface treatment following the plasma thermal spray process apparently delayed the severe oxidation process and surface spalling of the alloy. It was suggested that the slow reduction in weight in the post-laser-treated specimen was related to fewer defects in the coating layer. It was also found that a surface reaction layer formed through the diffusion of Fe into the Mo alloy substrate at high temperature. The layer mainly consisted of Fe-saturated Mo and FeMo intermetallic compounds. In order to observe the corrosion behavior of the laser-treated alloy in 3.5% NaCl solution, electrochemical characteristics were also investigated. A proposed equivalent circuit model for the specimen indicated localized corrosion of coated alloy with some permeable defects in the coating layer. Full article

(This article belongs to the Special Issue Intermetallics 2016)

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5493 KiB

Open AccessFeature PaperArticle

Numerical Evaluation of Temperature Field and Residual Stresses in an API 5L X80 Steel Welded Joint Using the Finite Element Method

by Jailson A. Da Nóbrega, Diego D. S. Diniz, Antonio A. Silva, Theophilo M. Maciel, Victor Hugo C. De Albuquerque and João Manuel R. S. Tavares

Metals 2016, 6(2), 28; https://doi.org/10.3390/met6020028 - 25 Jan 2016

Cited by 18 | Viewed by 6526

Abstract

Metallic materials undergo many metallurgical changes when subjected to welding thermal cycles, and these changes have a considerable influence on the thermo-mechanical properties of welded structures. One method for evaluating the welding thermal cycle variables, while still in the project phase, would be [...] Read more.

Metallic materials undergo many metallurgical changes when subjected to welding thermal cycles, and these changes have a considerable influence on the thermo-mechanical properties of welded structures. One method for evaluating the welding thermal cycle variables, while still in the project phase, would be simulation using computational methods. This paper presents an evaluation of the temperature field and residual stresses in a multipass weld of API 5L X80 steel, which is extensively used in oil and gas industry, using the Finite Element Method (FEM). In the simulation, the following complex phenomena were considered: the variation in physical and mechanical properties of the material as a function of the temperature, welding speed and convection and radiation mechanisms. Additionally, in order to characterize a multipass weld using the Gas Tungsten Arc Welding process for the root pass and the Shielded Metal Arc Welding process for the filling passes, the analytical heat source proposed by Goldak and Chakravarti was used. In addition, we were able to analyze the influence of the mesh refinement in the simulation results. The findings indicated a significant variation of about 50% in the peak temperature values. Furthermore, changes were observed in terms of the level and profile of the welded joint residual stresses when more than one welding pass was considered. Full article

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Metals, Volume 6, Issue 2 (February 2016) – 14 articles

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