Next Issue
Previous Issue

Table of Contents

Metals, Volume 9, Issue 6 (June 2019)

  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Readerexternal link to open them.
Cover Story (view full-size image) The individual solute atoms of Re and W are introduced in  matrix channels of Ni-base single [...] Read more.
View options order results:
result details:
Displaying articles 1-100
Export citation of selected articles as:
Open AccessArticle
Manufacturing of 42SiCr-Pipes for Quenching and Partitioning by Longitudinal HFI-Welding
Metals 2019, 9(6), 716; https://doi.org/10.3390/met9060716
Received: 13 May 2019 / Revised: 13 June 2019 / Accepted: 18 June 2019 / Published: 25 June 2019
Viewed by 365 | PDF Full-text (9094 KB) | HTML Full-text | XML Full-text
Abstract
In the pipe manufacturing and pipe processing industry, the demand for cost-effective pipes with high strength and good ductility is increasing. In the present study, the inductive longitudinal welding process was combined with a Quenching and Partitioning (Q&P) treatment to manufacture pipes with [...] Read more.
In the pipe manufacturing and pipe processing industry, the demand for cost-effective pipes with high strength and good ductility is increasing. In the present study, the inductive longitudinal welding process was combined with a Quenching and Partitioning (Q&P) treatment to manufacture pipes with enhanced mechanical properties. The aim of the Q&P process is to establish a martensitic structure with increased retained austenite content. This allows for the beneficial use of both phases: the strength of martensite as well as the ductility of retained austenite. A 42SiCr steel, developed for Q&P processes, was joined at the longitudinal seam by a high-frequency induction (HFI) welding process and was subsequently heat-treated. The applied heat treatments included normalizing, austenitizing, quenching, and two Q&P strategies (Q&P-A/Q&P-B) with distinct quenching (Tq = 200/150 °C) and partitioning temperatures (Tp = 300/250 °C). Investigations of the microstructures revealed that Q&P tubes exhibit increased amounts of retained austenite in the martensitic matrix. Differences between the weld junction and the base material occurred, especially regarding the morphology of the martensite; the martensite found in the weld junction is finer and corresponds more to the lath-type morphology, compared to the base material in the circumference. In all zones of the welded tube circumference, retained austenite has been found in similar distributions. The mechanical testing of the individual tubes demonstrated that the Q&P treatments offer increased strength compared to all other states and significantly improved ductility compared to the quenched condition. Therefore, the approach of Q&P treatment of HFI-welded tubes represents a route for the mass production of high-strength tubular products with improved ductility. Full article
(This article belongs to the Special Issue Advances in Metal Composites and Processing Technologies)
Figures

Figure 1

Open AccessArticle
Quasi-Static and Plate Impact Loading of Cast Magnesium Alloy ML5 Reinforced with Aluminum Nitride Nanoparticles
Metals 2019, 9(6), 715; https://doi.org/10.3390/met9060715
Received: 15 May 2019 / Revised: 12 June 2019 / Accepted: 20 June 2019 / Published: 25 June 2019
Viewed by 337 | PDF Full-text (4042 KB) | HTML Full-text | XML Full-text
Abstract
The influence of a small addition of 0.5 wt.% aluminum nitride nanoparticles with an average size of 80 nm on the mechanical properties of a cast magnesium alloy under quasi-static tensile (strain rate 10−4 s−1) and plate impact loading (strain [...] Read more.
The influence of a small addition of 0.5 wt.% aluminum nitride nanoparticles with an average size of 80 nm on the mechanical properties of a cast magnesium alloy under quasi-static tensile (strain rate 10−4 s−1) and plate impact loading (strain rate 105 s−1) was investigated. The composites were obtained by casting with a special mixing vortex device. After casting, some samples were subjected to heat treatment. The introduction of a small number of particles into the liquid metal led to a decrease in matrix grain size and a change in elasto-plastic and strength properties. Compared to quasi-static loading, the pre-heat treatment of tested alloys does not significantly affect the dynamic properties of a reinforced magnesium alloy under shock compression. Full article
(This article belongs to the Special Issue Production and Properties of Light Metal Matrix Nanocomposites)
Figures

Figure 1

Open AccessArticle
Controlling Nitrogen Dose Amount in Atmospheric-Pressure Plasma Jet Nitriding
Metals 2019, 9(6), 714; https://doi.org/10.3390/met9060714
Received: 25 April 2019 / Revised: 24 June 2019 / Accepted: 24 June 2019 / Published: 25 June 2019
Viewed by 326 | PDF Full-text (4546 KB) | HTML Full-text | XML Full-text
Abstract
A unique nitriding technique with the use of an atmospheric-pressure pulsed-arc plasma jet has been developed to offer a non-vacuum, easy-to-operate process of nitrogen doping to metal surfaces. This technique, however, suffered from a problem of excess nitrogen supply due to the high [...] Read more.
A unique nitriding technique with the use of an atmospheric-pressure pulsed-arc plasma jet has been developed to offer a non-vacuum, easy-to-operate process of nitrogen doping to metal surfaces. This technique, however, suffered from a problem of excess nitrogen supply due to the high pressure results in undesirable formation of voids and iron nitrides in the treated metal surface. To overcome this problem, we have first established a method to control the nitrogen dose amount supplied to the steel surface in the relevant nitriding technique. When the hydrogen fraction in the operating gas of nitrogen/hydrogen gas mixture increased from 1% up to 5%, the nitrogen density of the treated steel surface drastically decreased. As a result, the formation of voids were suppressed successfully. The controllability of the nitrogen dose amount is likely attributable to the density of NH radicals existing in the plume of the pulsed-arc plasma jet. Full article
(This article belongs to the Special Issue Plasmas Processes Applied on Metals and Alloys)
Figures

Graphical abstract

Open AccessArticle
Upward Unsteady-State Solidification of Dilute Al–Nb Alloys: Microstructure Characterization, Microhardness, Dynamic Modulus of Elasticity, Damping, and XRD Analyses
Metals 2019, 9(6), 713; https://doi.org/10.3390/met9060713
Received: 30 April 2019 / Revised: 4 June 2019 / Accepted: 5 June 2019 / Published: 25 June 2019
Viewed by 386 | PDF Full-text (7850 KB) | HTML Full-text | XML Full-text
Abstract
Aluminium alloys form many important structural components, and the addition of alloying elements contributes to the improvement of properties and characteristics. The objective of this work is to study the influence of thermal variables on the microstructure, present phases, microhardness, dynamic modulus of [...] Read more.
Aluminium alloys form many important structural components, and the addition of alloying elements contributes to the improvement of properties and characteristics. The objective of this work is to study the influence of thermal variables on the microstructure, present phases, microhardness, dynamic modulus of elasticity, and damping frequency in unidirectional solidification experiments, which were performed in situ during the manufacturing of Al–0.8 Nb and Al–1.2 Nb (wt.%) alloys. Experimental laws for the primary (λ1) and secondary (λ2) dendritic spacings for each alloy were given as a function of thermal variables. For Al–0.8%wt Nb, λ1 = 600.1( T ˙ )−1.85 and λ2 = 186.1(VL)−3.62; and for Al–1.2%wt Nb, λ1 = 133.6( T ˙ )−1.85 and λ2 = 55.6(VL)−3.62. Moreover, experimental growth laws that correlate the dendritic spacings are proposed. An increase in dendritic spacing influences the solidification kinetics observed, indicating that metal/mold interface distance or an increase in Nb content lowers the liquidus isotherm velocity (VL) and the cooling rate (). There is also a small increase in the microhardness, dynamic modulus of elasticity, and damping frequency in relation to the composition of the alloy and the microstructure. Full article
Figures

Figure 1

Open AccessArticle
Microstructural and Mechanical Properties of β-Type Ti–Nb–Sn Biomedical Alloys with Low Elastic Modulus
Metals 2019, 9(6), 712; https://doi.org/10.3390/met9060712
Received: 22 May 2019 / Revised: 14 June 2019 / Accepted: 21 June 2019 / Published: 25 June 2019
Viewed by 316 | PDF Full-text (4739 KB) | HTML Full-text | XML Full-text
Abstract
The microstructural and mechanical properties of β-type Ti85-xNb10+xSn5 (x = 0, 3, 6, 10 at.%) alloys with low elastic modulus were investigated. The experimental results show that the Ti85Nb10Sn5 and [...] Read more.
The microstructural and mechanical properties of β-type Ti85-xNb10+xSn5 (x = 0, 3, 6, 10 at.%) alloys with low elastic modulus were investigated. The experimental results show that the Ti85Nb10Sn5 and Ti75Nb20Sn5 alloys are composed of simple α and β phases, respectively; the Ti82Nb13Sn5 and Ti79Nb16Sn5 alloys are composed of β and α″ phases. The content of martensite phase decreases with the increase of Nb content. The Ti82Nb13Sn5 and Ti79Nb16Sn5 alloys show an inverse martensitic phase transition during heating. The Ti85Nb10Sn5 and Ti82Nb13Sn5 alloys with the small residual strain exhibit the good superelastic properties in 10-time cyclic loading. The reduced elastic modulus (Er) of the Ti75Nb20Sn5 alloy (61 GPa) measured by using the nanoindentation technique is 2–6 times of that of human bone (10–30 GPa), and is smaller than that of commercial Ti-6Al-4V biomedical alloy (120 GPa). The Ti75Nb20Sn5 alloy can be considered as a novel biomedical alloy. The wear resistance (H/Er) and anti-wear capability (H3/Er2) values of the four alloys are higher than those of the CP–Ti alloy (0.0238), which indicates that the present alloys have good wear resistance and anti-wear capability. Full article
Figures

Figure 1

Open AccessArticle
Cast Structure in Alloy A286, an Iron-Nickel Based Superalloy
Metals 2019, 9(6), 711; https://doi.org/10.3390/met9060711
Received: 24 May 2019 / Revised: 14 June 2019 / Accepted: 18 June 2019 / Published: 24 June 2019
Viewed by 252 | PDF Full-text (4144 KB) | HTML Full-text | XML Full-text
Abstract
The structure and segregation of a continuously cast iron-nickel based superalloy were investigated. Cross-sectional samples were prepared from the central section of a 150 × 150 mm square billet. The microporosity was measured from the surface to the center and theoretical conditions for [...] Read more.
The structure and segregation of a continuously cast iron-nickel based superalloy were investigated. Cross-sectional samples were prepared from the central section of a 150 × 150 mm square billet. The microporosity was measured from the surface to the center and theoretical conditions for pore formation were investigated. A central porosity, up to 10 mm in width, was present in the center of the billet. The measured secondary arm spacing was correlated with a calculated cooling rate and a mathematical model was obtained. Spinel particles were found in the structure, which acted as inoculation points for primary austenite and promoted the formation of the central equiaxed zone. Titanium segregated severely in the interdendritic areas and an increase of Ti most likely lead to a significant decrease in the hot ductility. Precipitates were detected in an area fraction of approximately 0.55% across the billet, which were identified as Ti(CN), TiN, η-Ni3Ti, and a phosphide phase. Full article
Figures

Figure 1

Open AccessArticle
Resistance Spot Welding of SUS316L Austenitic/SUS425 Ferritic Stainless Steels: Weldment Characteristics, Mechanical Properties, Phase Transformation and Solidification
Metals 2019, 9(6), 710; https://doi.org/10.3390/met9060710
Received: 9 May 2019 / Revised: 29 May 2019 / Accepted: 30 May 2019 / Published: 24 June 2019
Viewed by 268 | PDF Full-text (64121 KB) | HTML Full-text | XML Full-text
Abstract
This research examines the weldment characteristics and mechanical properties of lap joints of SUS316L/SUS425 stainless steels using resistance spot welding under variable weld currents and welding times. The weld current was varied between 7.0, 8.5, and 10.0 kA, and the welding time between [...] Read more.
This research examines the weldment characteristics and mechanical properties of lap joints of SUS316L/SUS425 stainless steels using resistance spot welding under variable weld currents and welding times. The weld current was varied between 7.0, 8.5, and 10.0 kA, and the welding time between 25, 38, and 50 cycles. The weldment quality characteristics under study were the depth of fusions, indentation depths, and nugget diameter, and the mechanical properties included the tensile shear force (TSF) and micro Vickers hardness. Phase transformation and solidification were characterized using scanning electron microscopy and energy dispersive X-ray spectrometry, together with Schaeffler and pseudo-binary predictive phase diagrams. The results revealed that the weldment quality was positively correlated with weld current and welding time, as were the TSF and micro hardness. The optimal welding condition was achieved under a 10.0 kA weld current and 25-cycle welding time. Under the optimal condition, the fusion zone exhibited compression-direction columnar grains consisting of austenite, ferrite, and martensite and the solidification was of ferrite plus Widmanstatten austenite. Full article
Figures

Figure 1

Open AccessArticle
Effect of Carbide Precipitation on the Evolution of Residual Stress during Tempering
Metals 2019, 9(6), 709; https://doi.org/10.3390/met9060709
Received: 6 June 2019 / Revised: 18 June 2019 / Accepted: 21 June 2019 / Published: 24 June 2019
Viewed by 257 | PDF Full-text (4198 KB) | HTML Full-text | XML Full-text
Abstract
The evolution of microstructure and residual stress during the tempering of 700 L low-carbon micro-alloyed steel was studied using a crack compliance method for measuring residual stress. Additionally, a non-isothermal tempering dilatation test, Vickers micro-hardness test, and transmission electron microscopy were used. The [...] Read more.
The evolution of microstructure and residual stress during the tempering of 700 L low-carbon micro-alloyed steel was studied using a crack compliance method for measuring residual stress. Additionally, a non-isothermal tempering dilatation test, Vickers micro-hardness test, and transmission electron microscopy were used. The evolution of residual stress during tempering consists of two stages. The first stage coincided with cementite precipitation. Under the initial residual stress, the transformation plasticity due to cementite precipitation leads to partial relaxation of the micro-stress evoked by the austenite-to-ferrite transformation during quenching. It also caused the material surface and the core to exhibit different residual stress evolution trends. After tempering at 300 C for 30 min, the residual stress was reduced from 487 MPa to 200 MPa; however, the elastic strain energy remained unchanged. The second stage coincided with alloy carbide precipitation and Mn partitioning, but the precipitation of the alloy carbide only reduced the elastic strain energy by 8.7%. Thus, the change in activation energy was the main reason for the relaxation of residual stress at this stage. After tempering at 600 C for 30 min, the residual stress was reduced to 174 MPa, the elastic strain energy was reduced by 72.72%, and the residual stress was controlled. Full article
Figures

Figure 1

Open AccessArticle
Synthesis of Nanosilica via Olivine Mineral Carbonation under High Pressure in an Autoclave
Metals 2019, 9(6), 708; https://doi.org/10.3390/met9060708
Received: 24 May 2019 / Revised: 18 June 2019 / Accepted: 19 June 2019 / Published: 24 June 2019
Viewed by 324 | PDF Full-text (6715 KB) | HTML Full-text | XML Full-text
Abstract
Silicon dioxide nanoparticles, also known as silica nanoparticles or nanosilica, are the basis for a great deal of biomedical and catalytic research due to their stability, low toxicity and ability to be functionalized with a range of molecules and polymers. A novel synthesis [...] Read more.
Silicon dioxide nanoparticles, also known as silica nanoparticles or nanosilica, are the basis for a great deal of biomedical and catalytic research due to their stability, low toxicity and ability to be functionalized with a range of molecules and polymers. A novel synthesis route is based on CO2 absorption/sequestration in an autoclave by forsterite (Mg2SiO4), which is part of the mineral group of olivines. Therefore, it is a feasible and safe method to bind carbon dioxide in carbonate compounds such as magnesite forming at the same time as the spherical particles of silica. Indifference to traditional methods of synthesis of nanosilica such as sol gel, ultrasonic spray pyrolysis method and hydrothermal synthesis using some acids and alkaline solutions, this synthesis method takes place in water solution at 175 °C and above 100 bar. Our first experiments have studied the influence of some additives such as sodium bicarbonate, oxalic acid and ascorbic acid, solid/liquid ratio and particle size on the carbonation efficiency, without any consideration of formed silica. This paper focuses on a carbonation mechanism for synthesis of nanosilica under high pressure and high temperature in an autoclave, its morphological characteristics and important parameters for silica precipitation such as pH-value and rotating speed. Full article
(This article belongs to the Special Issue Advances in Synthesis of Metallic, Oxidic and Composite Powders)
Figures

Figure 1

Open AccessArticle
Determination of Grain Growth Kinetics and Assessment of Welding Effect on Properties of S700MC Steel in the HAZ of Welded Joints
Metals 2019, 9(6), 707; https://doi.org/10.3390/met9060707
Received: 30 May 2019 / Revised: 12 June 2019 / Accepted: 18 June 2019 / Published: 24 June 2019
Viewed by 330 | PDF Full-text (6994 KB) | HTML Full-text | XML Full-text
Abstract
The welding of fine-grained steels is a very specific technology because of the requirement for the heat input limit value. Applying temperature cycles results in an intense grain growth in a high-temperature heat-affected zone (HAZ). This has a significant effect on the changing [...] Read more.
The welding of fine-grained steels is a very specific technology because of the requirement for the heat input limit value. Applying temperature cycles results in an intense grain growth in a high-temperature heat-affected zone (HAZ). This has a significant effect on the changing of strength properties and impact values. The intensity of grain coarsening in the HAZ can be predicted based on the experimentally determined activation energy and material constant, both of which define grain growth kinetics. These quantities, together with real measured welding cycles, can be subsequently used during experiments to determine mechanical properties in a high-temperature HAZ. This paper shows a methodical procedure leading to the obtainment of the material quantities mentioned above that define the grain growth, both at fast and slow temperature cycles. These data were used to define the exposure temperature and the soaking time in a vacuum furnace to prepare test samples with grain sizes corresponding to the high-temperature HAZ of welded joints for the testing procedures. Simultaneously, by means of the thermo-mechanical simulator Gleeble 3500, testing samples were prepared which, due to a temperature gradient, created conditions comparable to those in the HAZ. The experiments were both carried out with the possibility of free sample dilatation and under a condition of zero dilation, which happens when the thermal expansion of a material is compensated by plastic deformation. It has been found that shape of the temperature cycle, maximal achieved cycle temperature, cooling rate, and, particularly, the time in which the sample is in the austenite region have significant effects on the resulting change of properties. Full article
(This article belongs to the Special Issue High-Strength Low-Alloy Steels)
Figures

Figure 1

Open AccessArticle
Tensile Properties and Corrosion Resistance of Al-xFe-La Alloys for Aluminium Current Collector of Lithium-Ion Batteries
Metals 2019, 9(6), 706; https://doi.org/10.3390/met9060706
Received: 30 May 2019 / Revised: 13 June 2019 / Accepted: 18 June 2019 / Published: 24 June 2019
Viewed by 338 | PDF Full-text (6274 KB) | HTML Full-text | XML Full-text
Abstract
Al-xFe-La alloys (x = 0.07, 0.1, 0.2) for aluminum current collectors of lithium-ion batteries were prepared and the microstructure of Al-0.07Fe-0.07La, Al-0.1Fe-0.07La and Al-0.2Fe-0.07La aluminum alloys were observed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS). The experimental results showed that with [...] Read more.
Al-xFe-La alloys (x = 0.07, 0.1, 0.2) for aluminum current collectors of lithium-ion batteries were prepared and the microstructure of Al-0.07Fe-0.07La, Al-0.1Fe-0.07La and Al-0.2Fe-0.07La aluminum alloys were observed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS). The experimental results showed that with the increase of Fe content, the size of the second phases in Al-xFe-0.07La alloys became finer and more dispersed and that the microstructure of the alloy had improved. The strength and corrosion resistance of Al-xFe-La alloys were studied by tensile tests and electrochemical tests and the morphological investigations of samples were also conducted by SEM and EDS. With the increase of Fe content, the strength and corrosion resistance of Al-xFe-La alloys became better. Compared to Al-0.07Fe-0.07La alloy, the yield strength and tensile strength of the Al-0.2Fe-0.07La alloy increased by 51.19% and 58.48% respectively, and the elongation increased by 88.41%. Moreover, Al-0.2Fe-0.07La alloy had much more positive corrosion potential and much smaller corrosion current than those of Al-0.07Fe-0.07La alloy. Full article
(This article belongs to the Special Issue Advances in Characterization of Heterogeneous Metals/Alloys)
Figures

Figure 1

Open AccessArticle
Development of a Cr-Ni-V-N Medium Manganese Steel with Balanced Mechanical and Corrosion Properties
Metals 2019, 9(6), 705; https://doi.org/10.3390/met9060705
Received: 15 May 2019 / Revised: 10 June 2019 / Accepted: 19 June 2019 / Published: 22 June 2019
Viewed by 427 | PDF Full-text (3246 KB) | HTML Full-text | XML Full-text
Abstract
A novel medium manganese (MMn) steel with additions of Cr (18%), Ni (5%), V (1%), and N (0.3%) was developed in order to provide an enhanced corrosion resistance along with a superior strength–ductility balance. The laboratory melted ingots were hot rolled, cold rolled, [...] Read more.
A novel medium manganese (MMn) steel with additions of Cr (18%), Ni (5%), V (1%), and N (0.3%) was developed in order to provide an enhanced corrosion resistance along with a superior strength–ductility balance. The laboratory melted ingots were hot rolled, cold rolled, and finally annealed at 1000 °C for 3 min. The recrystallized single-phase austenitic microstructure consisted of ultrafine grains (~1.3 µm) with a substantial amount of Cr- and V-based precipitates in a bimodal particle size distribution (100–400 nm and <20 nm). The properties of the newly developed austenitic MMn steel X20CrNiMnVN18-5-10 were compared with the standard austenitic stainless steel X5CrNi18-8 and with the austenitic twinning-induced plasticity (TWIP) steel X60MnAl17-1. With a total elongation of 45%, the MMn steel showed an increase in yield strength by 300 MPa and in tensile strength by 150 MPa in comparison to both benchmark steels. No deformation twins were observed even after fracture for the MMn steel, which emphasizes the role of the grain size and precipitation-induced change in the austenite stability in controlling the deformation mechanism. The potentio-dynamic polarization measurements in 5% NaCl revealed a very low current density value of 7.2 × 10−4 mA/cm2 compared to that of TWIP steel X60MnAl17-1 of 8.2 × 10−3 mA/cm2, but it was relatively higher than that of stainless steel X5CrNi18-8 of 2.0 × 10−4 mA/cm2. This work demonstrates that the enhanced mechanical properties of the developed MMn steel are tailored by maintaining an ultrafine grain microstructure with a significant amount of nanoprecipitates, while the high corrosion resistance in 5% NaCl solution is attributed to the high Cr and N contents as well as to the ultrafine grain size. Full article
(This article belongs to the Special Issue Physical Metallurgy of High Manganese Steels)
Figures

Figure 1

Open AccessArticle
Fatigue Behavior of Metastable Austenitic Stainless Steels in LCF, HCF and VHCF Regimes at Ambient and Elevated Temperatures
Metals 2019, 9(6), 704; https://doi.org/10.3390/met9060704
Received: 31 May 2019 / Revised: 18 June 2019 / Accepted: 19 June 2019 / Published: 21 June 2019
Viewed by 427 | PDF Full-text (22168 KB) | HTML Full-text | XML Full-text
Abstract
Corrosion resistance has been the main scope of the development in high-alloyed low carbon austenitic stainless steels. However, the chemical composition influences not only the passivity but also significantly affects their metastability and, consequently, the transformation as well as the cyclic deformation behavior. [...] Read more.
Corrosion resistance has been the main scope of the development in high-alloyed low carbon austenitic stainless steels. However, the chemical composition influences not only the passivity but also significantly affects their metastability and, consequently, the transformation as well as the cyclic deformation behavior. In technical applications, the austenitic stainless steels undergo fatigue in low cycle fatigue (LCF), high cycle fatigue (HCF), and very high cycle fatigue (VHCF) regime at room and elevated temperatures. In this context, the paper focuses on fatigue and transformation behavior at ambient temperature and 300 °C of two batches of metastable austenitic stainless steel AISI 347 in the whole fatigue regime from LCF to VHCF. Fatigue tests were performed on two types of testing machines: (i) servohydraulic and (ii) ultrasonic with frequencies: at (i) 0.01 Hz (LCF), 5 and 20 Hz (HCF) and 980 Hz (VHCF); and at (ii) with 20 kHz (VHCF). The results show the significant influence of chemical composition and temperature of deformation induced α´-martensite formation and cyclic deformation behavior. Furthermore, a “true” fatigue limit of investigated metastable austenitic stainless steel AISI 347 was identified including the VHCF regime at ambient temperature and elevated temperatures. Full article
(This article belongs to the Special Issue Advances in Low-carbon and Stainless Steels)
Figures

Graphical abstract

Open AccessArticle
Optimization of the Continuous Galvanizing Heat Treatment Process in Ultra-High Strength Dual Phase Steels Using a Multivariate Model
Metals 2019, 9(6), 703; https://doi.org/10.3390/met9060703
Received: 26 April 2019 / Accepted: 4 May 2019 / Published: 21 June 2019
Viewed by 382 | PDF Full-text (2815 KB) | HTML Full-text | XML Full-text
Abstract
The main process variables to produce galvanized dual phase (DP) steel sheets in continuous galvanizing lines are time and temperature of intercritical austenitizing (tIA and TIA), cooling rate (CR1) after intercritical austenitizing, holding time at the [...] Read more.
The main process variables to produce galvanized dual phase (DP) steel sheets in continuous galvanizing lines are time and temperature of intercritical austenitizing (tIA and TIA), cooling rate (CR1) after intercritical austenitizing, holding time at the galvanizing temperature (tG) and finally the cooling rate (CR2) to room temperature. In this research work, the effects of CR1, tG and CR2 on the ultimate tensile strength (UTS), yield strength (YS), and elongation (EL) of cold rolled low carbon steel were investigated by applying an experimental central composite design and a multivariate regression model. A multi-objective optimization and the Pareto Front were used for the optimization of the continuous galvanizing heat treatments. Typical thermal cycles applied for the production of continuous galvanized AHSS-DP strips were simulated in a quenching dilatometer using miniature tensile specimens. The experimental results of UTS, YS and EL were used to fit the multivariate regression model for the prediction of these mechanical properties from the processing parameters (CR1, tG and CR2). In general, the results show that the proposed multivariate model correctly predicts the mechanical properties of UTS, YS and %EL for DP steels processed under continuous galvanizing conditions. Furthermore, it is demonstrated that the phase transformations that take place during the optimized tG (galvanizing time) play a dominant role in determining the values of the mechanical properties of the DP steel. The production of hot-dip galvanized DP steels with a minimum tensile strength of 1100 MPa is possible by applying the proposed methodology. The results provide important scientific and technological knowledge about the annealing/galvanizing thermal cycle effects on the microstructure and mechanical properties of DP steels. Full article
(This article belongs to the Special Issue Numerical Modelling and Simulation of Metal Processing)
Figures

Figure 1

Open AccessArticle
Transient Evolution of Inclusions during Al and Ti Additions in Fe-20 Mass pct Cr Alloy
Metals 2019, 9(6), 702; https://doi.org/10.3390/met9060702
Received: 27 May 2019 / Revised: 13 June 2019 / Accepted: 19 June 2019 / Published: 21 June 2019
Viewed by 391 | PDF Full-text (34196 KB) | HTML Full-text | XML Full-text
Abstract
The transient evolution of inclusions during Al and Ti additions in a Fe-20 mass pct Cr alloy was investigated using polished cross sections and electrolytic extraction. After Al addition, the evolution of Al2O3-based inclusions based upon the area and [...] Read more.
The transient evolution of inclusions during Al and Ti additions in a Fe-20 mass pct Cr alloy was investigated using polished cross sections and electrolytic extraction. After Al addition, the evolution of Al2O3-based inclusions based upon the area and particle size passed through the following three main stages with time: Particle agglomeration, inclusion floating, and a slow decrease of the remaining Al2O3-based inclusions. Titanium wire was fed into the steel at the end of the floating stage after Al addition when the Ostwald ripening process was finished. Immediately after Ti addition, the transient phase of Ti oxide was readily generated on the existing Al2O3-based inclusion and disappeared due to Al reduction as time progressed. The formation of the transient TiOx phase was affected by the low disregistry between Al2O3 and TiOx and the local Ti supersaturation, which cannot be predicted by the equilibrium relations of Ti–O–N or Ti–Al–O in the high-Cr-containing melt. Because of the local supersaturation of dissolved [%Ti] and [%N] shortly after Ti addition, TiN associated with existing inclusions and three types of individual TiN including single cubes, twinned inclusions, and clusters were identified. In order to minimize the Ti loss caused by the formation of Ti-rich zones during the transient stages, the removal of large Al2O3-based particles including aggregates, clusters, and flower-shaped inclusions should be promoted by stirring before Ti addition. After Ti addition, Brownian and turbulent were the major factors affecting the collision of particles smaller than the threshold of 2.7 μm. The agglomeration of inclusions larger than this threshold was mainly dominated by turbulent and Stokes’ collisions. Full article
Figures

Figure 1

Open AccessArticle
Preparation of a Master Fe–Cu Alloy by Smelting of a Cu-Bearing Direct Reduction Iron Powder
Metals 2019, 9(6), 701; https://doi.org/10.3390/met9060701
Received: 13 May 2019 / Revised: 13 June 2019 / Accepted: 18 June 2019 / Published: 21 June 2019
Viewed by 329 | PDF Full-text (4285 KB) | HTML Full-text | XML Full-text
Abstract
Generally, the Cu-bearing direct reduction iron powder (CBDRI) obtained from a direct reduction-magnetic separation process of waste copper slag contains a high content of impurities and cannot be directly used to produce Cu-bearing special steel. In this paper, further smelting treatment of CBDRI [...] Read more.
Generally, the Cu-bearing direct reduction iron powder (CBDRI) obtained from a direct reduction-magnetic separation process of waste copper slag contains a high content of impurities and cannot be directly used to produce Cu-bearing special steel. In this paper, further smelting treatment of CBDRI was conducted to remove its impurities (such as S, SiO2, Al2O3, CaO and MgO) and acquire a high-quality Fe–Cu master alloy. The results show that the Fe–Cu master alloy, assaying 95.9% Fe, 1.4% Cu and minor impurities, can be obtained from the smelting process at 1550 °C for 40 min with 1.0 basicity. Meanwhile, the corresponding iron and copper recoveries are 98.6% and 97.2%, respectively. Theoretical calculations and experimental results show that appropriate basicity (0.9~1.1) is beneficial for the recovery of Fe and Cu from a thermodynamic viewpoint due to the excellent fluidity of the slag in this basicity range. Moreover, the mechanism of desulfurization was revealed by calculating the sulfide capacity and the desulfurization reaction kinetics. Increasing the binary basicity of the slag benefits both the sulfide capacity and diffusion coefficient of the sulfur in the molten slag, resulting in higher desulfurization efficiency and lower S content in the master alloy. Full article
Figures

Graphical abstract

Open AccessArticle
The Effect of Temperature and Mo Content on the Lattice Misfit of Model Ni-Based Superalloys
Metals 2019, 9(6), 700; https://doi.org/10.3390/met9060700
Received: 28 April 2019 / Revised: 16 June 2019 / Accepted: 18 June 2019 / Published: 21 June 2019
Viewed by 362 | PDF Full-text (3803 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The lattice parameters and misfit of the γ and γ′ phases in a series of model quaternary Ni-based superalloys with and without Mo additions have been determined using neutron diffraction between room temperature and 700 °C. Despite the fact that Mo is typically [...] Read more.
The lattice parameters and misfit of the γ and γ′ phases in a series of model quaternary Ni-based superalloys with and without Mo additions have been determined using neutron diffraction between room temperature and 700 °C. Despite the fact that Mo is typically expected to partition almost exclusively to the γ phase and thereby increase the lattice parameter of that phase alone, the lattice parameters of both the γ and γ′ phases were observed to increase with Mo addition. Nevertheless, the effect on the γ lattice parameter was more pronounced, leading to an overall decrease in the lattice misfit with increasing Mo content. Alloys with the lowest Mo content were found to be positively misfitting, whilst additions of 5 at.% Mo produced a negative lattice misfit. A general decrease in the lattice misfit with increasing temperature was also observed. Full article
Figures

Graphical abstract

Open AccessFeature PaperArticle
Continuous Electron Beam Post-Treatment of EBF3-Fabricated Ti–6Al–4V Parts
Metals 2019, 9(6), 699; https://doi.org/10.3390/met9060699
Received: 23 May 2019 / Revised: 15 June 2019 / Accepted: 19 June 2019 / Published: 21 June 2019
Viewed by 421 | PDF Full-text (8675 KB) | HTML Full-text | XML Full-text
Abstract
In the present study, the methods of optical, scanning electron, and transmission electron microscopy as well as X-ray diffraction analysis gained insights into the mechanisms of surface finish and microstructure formation of Ti–6Al–4V parts during an EBF3-process. It was found that [...] Read more.
In the present study, the methods of optical, scanning electron, and transmission electron microscopy as well as X-ray diffraction analysis gained insights into the mechanisms of surface finish and microstructure formation of Ti–6Al–4V parts during an EBF3-process. It was found that the slip band propagation within the outermost surface layer provided dissipation of the stored strain energy associated with martensitic transformations. The latter caused the lath fragmentation as well as precipitation of nanosized β grains and an orthorhombic martensite α″ phase at the secondary α lath boundaries of as-built Ti–6Al–4V parts. The effect of continuous electron beam post-treatment on the surface finish, microstructure, and mechanical properties of EBF3-fabricated Ti–6Al–4V parts was revealed. The brittle outermost surface layer of the EBF3-fabricated samples was melted upon the treatment, resulting in the formation of equiaxial prior β grains of 20 to 30 μm in size with the fragmented acicular α′ phase. Electron-beam irradiation induced transformations within the 70 μm thick molten surface layer and 500 μm thick heat affected zone significantly increased the Vickers microhardness and tensile strength of the EBF3-fabricated Ti–6Al–4V samples. Full article
(This article belongs to the Special Issue Titanium Alloys: Processing and Properties)
Figures

Figure 1

Open AccessFeature PaperArticle
Comparative Study of Chip Formation in Orthogonal and Oblique Slow-Rate Machining of EN 16MnCr5 Steel
Metals 2019, 9(6), 698; https://doi.org/10.3390/met9060698
Received: 23 May 2019 / Revised: 15 June 2019 / Accepted: 18 June 2019 / Published: 20 June 2019
Viewed by 403 | PDF Full-text (6054 KB) | HTML Full-text | XML Full-text
Abstract
In today’s unmanned productions systems, it is very important that the manufacturing processes are carried out efficiently and smoothly. Therefore, controlling chip formation becomes an essential issue to be dealt with. It can be said that the material removal from a workpiece using [...] Read more.
In today’s unmanned productions systems, it is very important that the manufacturing processes are carried out efficiently and smoothly. Therefore, controlling chip formation becomes an essential issue to be dealt with. It can be said that the material removal from a workpiece using machining is based on the degradation of material cohesion made in a controlled manner. The aim of the study was to understand the chip formation mechanisms that can, during uncontrolled processes, result in the formation and propagation of microcracks on the machined surface and, as such, cause failure of a component during its operation. This article addresses some aspects of chip formation in the orthogonal and oblique slow-rate machining of EN 16MnCr5 steel. In order to avoid chip root deformation and its thermal influence on sample acquisition, that could cause the changes in the microstructure of material, a new reliable method for sample acquisition has been developed in this research. The results of the experiments have been statistically processed. The obtained dependencies have uncovered how the cutting tool geometry and cutting conditions influence a chip shape, temperature in cutting area, or microhardness according to Vickers in the area of shear angle. Full article
(This article belongs to the Special Issue Failure Mechanisms in Alloys)
Figures

Figure 1

Open AccessArticle
Accuracy and Surface Quality Improvements in the Manufacturing of Ti-6Al-4V Parts Using Hot Single Point Incremental Forming
Metals 2019, 9(6), 697; https://doi.org/10.3390/met9060697
Received: 23 May 2019 / Revised: 12 June 2019 / Accepted: 18 June 2019 / Published: 20 June 2019
Viewed by 502 | PDF Full-text (13696 KB) | HTML Full-text | XML Full-text
Abstract
The present work focuses on the manufacturing of Ti-6Al-4V parts using hot single point incremental forming (SPIF), a non-conventional forming technology mainly oriented toward the fabrication of prototypes, spare parts, or very low volume series. In the used procedure, the entire sheet is [...] Read more.
The present work focuses on the manufacturing of Ti-6Al-4V parts using hot single point incremental forming (SPIF), a non-conventional forming technology mainly oriented toward the fabrication of prototypes, spare parts, or very low volume series. In the used procedure, the entire sheet is heated and kept at uniform temperature while the tool incrementally forms the part, with the limited accuracy of the obtained parts being the major drawback of the process. Thus, this work proposes two approaches to improve the geometric accuracy of Ti-6Al-4V SPIF parts: (i) correct the tool path by applying an intelligent process model (IPM) that counteracts deviations associated with the springback, and (ii) skip overforming deviations associated with the deflection of the sheet along the perimeter of the part based on a design improvement. For this purpose, a generic asymmetric design that incorporates features of a typical aerospace Ti-6Al-4V part is used. The results point out the potential of both solutions to significantly improve the accuracy of the parts. The application of the IPM model leads to an accuracy improvement up to 49%, whereas a 25.4% improvement can be attributed to the addendum introduction. The geometric accuracy study includes the two finishing operations needed to obtain the part, namely decontamination and trimming. Full article
(This article belongs to the Special Issue New Processes and Machine Tools for Advanced Metal Alloys)
Figures

Figure 1

Open AccessArticle
Effect Range of the Material Constraint-II. Interface Crack
Metals 2019, 9(6), 696; https://doi.org/10.3390/met9060696
Received: 1 June 2019 / Revised: 16 June 2019 / Accepted: 18 June 2019 / Published: 20 June 2019
Viewed by 307 | PDF Full-text (3741 KB) | HTML Full-text | XML Full-text
Abstract
The selection of fracture behaviors used in the structure integrity assessment has significant implications on the accuracy of the assessment. The effect range of the material constraint is an important factor which effects the fracture behaviors of structures and exists in the different [...] Read more.
The selection of fracture behaviors used in the structure integrity assessment has significant implications on the accuracy of the assessment. The effect range of the material constraint is an important factor which effects the fracture behaviors of structures and exists in the different kinds of welded joints with the center crack. However, for the material constraint induced by an interface crack, which also appears widely in the welded joints, it is not clear whether the effect range exists or not. The further study of the effect range of the material constraint for the welded joints with interface crack is meaningful. Thus, in this study, different basic models with interface crack were designed, the fracture behaviors of these basic models under different material constraints were calculated, and the effect range of the material constraint induced by interface crack were studied. This study about the interface crack and the previous study about the center crack provide an additional basis for an accurate structure integrity assessment. Full article
Figures

Figure 1

Open AccessArticle
Processing–Microstructure Relation of Deformed and Partitioned (D&P) Steels
Metals 2019, 9(6), 695; https://doi.org/10.3390/met9060695
Received: 22 May 2019 / Revised: 18 June 2019 / Accepted: 19 June 2019 / Published: 20 June 2019
Viewed by 454 | PDF Full-text (3646 KB) | HTML Full-text | XML Full-text
Abstract
An ultrastrong and ductile deformed and partitioned (D&P) steel developed by dislocation engineering has been reported recently. However, the microstructure evolution during the D&P processes has not yet been fully understood. The present paper aims to elucidate the process–microstructure relation in D&P process. [...] Read more.
An ultrastrong and ductile deformed and partitioned (D&P) steel developed by dislocation engineering has been reported recently. However, the microstructure evolution during the D&P processes has not yet been fully understood. The present paper aims to elucidate the process–microstructure relation in D&P process. Specifically, the evolution of phase fraction and microstructure during the corresponding D&P process are captured by means of X-ray diffraction (XRD) and electron backscatter diffraction (EBSD). Subsequently, the effect of partitioning temperature on dislocation density and mechanical properties of D&P steel is investigated with the assistance of uniaxial tensile tests and synchrotron X-ray diffraction. It is found that a heterogeneous microstructure is firstly realized by hot rolling. The warm rolling is crucial in introducing dislocations, while deformation-induced martensite is mainly formed during cold rolling. The dislocation density of the D&P steel gradually decreases with the increase of partitioning temperature, while the high yield strength is maintained owing to the bake hardening. The ductility is firstly enhanced while then deteriorated by increasing partitioning temperature due to the strong interaction between dislocation and interstitial atoms at higher partitioning temperatures. Full article
(This article belongs to the Special Issue Physical Metallurgy of High Manganese Steels)
Figures

Figure 1

Open AccessArticle
Springback Prediction of a Hot Stamping Component Based on the Area Fractions of Phases
Metals 2019, 9(6), 694; https://doi.org/10.3390/met9060694
Received: 31 May 2019 / Revised: 13 June 2019 / Accepted: 14 June 2019 / Published: 20 June 2019
Viewed by 395 | PDF Full-text (2770 KB) | HTML Full-text | XML Full-text
Abstract
Different from traditional hot stamping components with full martensite, the new tailored hot stamping (THS) components have different quenched microstructures, which results in their lower shape accuracy. To investigate the influence of different quenched phases on the springback of a component, a THS [...] Read more.
Different from traditional hot stamping components with full martensite, the new tailored hot stamping (THS) components have different quenched microstructures, which results in their lower shape accuracy. To investigate the influence of different quenched phases on the springback of a component, a THS experiment of a U-shaped component was performed with segmented heating and a cooling tool. The area fractions of phases at different tool temperatures were obtained by a two-stage color tint etching procedure. Results showed that the quenched phase of the cold zone was almost full martensite. The area fraction of martensite in the hot zone was reduced to the lowest 13% at the tool temperature of 600 °C, while the bainite content reached the highest at 70%. The springback angles at different tool temperatures for quenching were measured by 3D scanning technology and the reverse modeling method. It was revealed that the springback angle increased with the increase of martensite and yet decreased with the increase of bainite. The relationship between the springback angle and the area fractions of the quenched phases was established by means of multiple linear regression analyses. The error analysis results of the predictions and measurements showed that the springback analysis model, based on the area fractions of quenched phases, could be used to predict the springback of hot stamping components with tailored properties. Full article
Figures

Figure 1

Open AccessArticle
Mathematical Modelling of the Initial Mold Filling with Utilization of an Angled Runner
Metals 2019, 9(6), 693; https://doi.org/10.3390/met9060693
Received: 20 May 2019 / Revised: 7 June 2019 / Accepted: 15 June 2019 / Published: 19 June 2019
Viewed by 386 | PDF Full-text (3036 KB) | HTML Full-text | XML Full-text
Abstract
The flow pattern plays a crucial role in the uphill teeming process. The non-metallic inclusion generation due to interaction with the mold flux is believed to be influenced by the flow pattern. In this study, a three-dimensional mathematical model of the filling of [...] Read more.
The flow pattern plays a crucial role in the uphill teeming process. The non-metallic inclusion generation due to interaction with the mold flux is believed to be influenced by the flow pattern. In this study, a three-dimensional mathematical model of the filling of a gating system for 10, 20, and 30 degrees angled runners was used to predict the fluid flow characteristics. Moreover, a mathematical model with a horizontal runner was applied as a reference. The predictions indicate that the angled-runner-design decreases the hump height during the initial filling stage, which results in less entrapment of mold flux into the mold. Nevertheless, increasing the angle of runner can result in a lower hump height, while the 30 degree angled runner gives a much more stable increase of the hump height during the initial filling stage. Besides CFD calculations, some thermodynamic calculations are taken into account for the chemical reactions between liquid steel and gas. The results show that the bubble shrinks due to the fact that N and O are dissolved into steel. The present findings strongly suggest that changing the horizontal runner to an angled runner would be an effective means of reducing flow unevenness during the initial filling of ingots, if the added steel losses are deemed acceptable. Full article
Figures

Figure 1

Open AccessArticle
Influence of Different Annealing Atmospheres on the Mechanical Properties of Freestanding MCrAlY Bond Coats Investigated by Micro-Tensile Creep Tests
Metals 2019, 9(6), 692; https://doi.org/10.3390/met9060692
Received: 22 May 2019 / Revised: 16 June 2019 / Accepted: 17 June 2019 / Published: 19 June 2019
Viewed by 439 | PDF Full-text (4776 KB) | HTML Full-text | XML Full-text
Abstract
The mechanical properties of low-pressure plasma sprayed (LPPS) MCrAlY (M = Ni, Co) bond coats, Amdry 386, Amdry 9954 and oxide dispersion strengthened (ODS) Amdry 9954 (named Amdry 9954 + ODS) were investigated after annealing in three atmospheres: Ar–O2, Ar–H2 [...] Read more.
The mechanical properties of low-pressure plasma sprayed (LPPS) MCrAlY (M = Ni, Co) bond coats, Amdry 386, Amdry 9954 and oxide dispersion strengthened (ODS) Amdry 9954 (named Amdry 9954 + ODS) were investigated after annealing in three atmospheres: Ar–O2, Ar–H2O, and Ar–H2–H2O. Freestanding bond coats were investigated to avoid any influence from the substrate. Miniaturized cylindrical tensile specimens were produced by a special grinding process and then tested in a thermomechanical analyzer (TMA) within a temperature range of 900–950 °C. Grain size and phase fraction of all bond coats were investigated by EBSD before testing and no difference in microstructure was revealed due to annealing in various atmospheres. The influence of annealing in different atmospheres on the creep strength was not very pronounced for the Co-based bond coats Amdry 9954 and Amdry 9954 + ODS in the tested conditions. The ODS bond coats revealed significantly higher creep strength but a lower strain to failure than the ODS-free Amdry 9954. The Ni-based bond coat Amdry 386 showed higher creep strength than Amdry 9954 due to the higher fraction of the β-NiAl phase. Additionally, its creep properties at 900 °C were much more affected by annealing in different atmospheres. The bond coat Amdry 386 annealed in an Ar–H2O atmosphere showed a significantly lower creep rate than the bond coat annealed in Ar–O2 and Ar–H2–H2O atmospheres. Full article
(This article belongs to the Special Issue Creep and High Temperature Deformation of Metals and Alloys)
Figures

Figure 1

Open AccessArticle
Interface Behavior and Impact Properties of Dissimilar Al/Steel Keyhole-Free FSSW Joints
Metals 2019, 9(6), 691; https://doi.org/10.3390/met9060691
Received: 28 April 2019 / Revised: 11 June 2019 / Accepted: 13 June 2019 / Published: 18 June 2019
Viewed by 380 | PDF Full-text (8687 KB) | HTML Full-text | XML Full-text
Abstract
This work systematically investigates the interface behavior and impact properties of the keyhole-free friction stir spot welding (FSSW) of a dissimilar metal AA6082-T4 Al alloy and DP600 galvanized steel. The keyhole is eliminated by pin retraction technology. The welding process is in accordance [...] Read more.
This work systematically investigates the interface behavior and impact properties of the keyhole-free friction stir spot welding (FSSW) of a dissimilar metal AA6082-T4 Al alloy and DP600 galvanized steel. The keyhole is eliminated by pin retraction technology. The welding process is in accordance with the welding temperature curve and the maximum temperature of the periphery of the shoulder, measured at about 500 °C. The transition layers were formed at the interface, in which the Al, Fe, and Zn elements form an inhomogeneous diffusion. A cloud cluster-like mechanical mixing of the Al and steel components is formed in the stirring zone. The impact toughness of the specimen with a welding parameter of 1000 rpm is the best. To a certain extent, the factors affecting the impact energy are not the maximum impact load but the maximum impact deformation. The maximum impact deformation directly reflects the post-crack propagation energy, which significantly affects its impact toughness. In addition, the impact fracture showed a mixed ductile and brittle fracture mode with a brittle–ductile transition zone. Most of the impact energy was absorbed by the ductile fracture. Full article
(This article belongs to the Special Issue Characterization of Welded Joints)
Figures

Graphical abstract

Open AccessArticle
Microstructure Characterization and Mechanical Property of Mg/Al Laminated Composite Prepared by the Novel Approach: Corrugated + Flat Rolling (CFR)
Metals 2019, 9(6), 690; https://doi.org/10.3390/met9060690
Received: 28 May 2019 / Revised: 9 June 2019 / Accepted: 13 June 2019 / Published: 17 June 2019
Viewed by 507 | PDF Full-text (12899 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, Mg/Al laminated composites were successfully prepared at 400 °C by corrugated + flat rolling (CFR) with reduction ratios of 35% and 25% and subsequent annealing treatments were conducted at 200–350 °C for 30 min. A two-dimensional model was established to [...] Read more.
In this paper, Mg/Al laminated composites were successfully prepared at 400 °C by corrugated + flat rolling (CFR) with reduction ratios of 35% and 25% and subsequent annealing treatments were conducted at 200–350 °C for 30 min. A two-dimensional model was established to analyze the strain distribution during the first corrugated rolling process. Simulation results indicated that severe plastic deformation was formed at trough positions, which included more numerous refined grains than in the peak positions. The interfacial microstructure and mechanical property of the flattened composites along the rolling direction (RD) and the transverse direction (TD) were investigated. The results revealed that longitudinal discontinuous and transverse continuous interfacial intermetallic compounds (IMCs) were observed of the flattened as-rolled sample. Spatial distribution was provided for the grain microstructure along the thickness and rolling direction for AZ31B magnesium alloys of the CFR as-rolled composite. Mechanical property results showed that the longitudinal ultimate tensile strength (UTS) and elongation (EL) of the as-rolled sample reached 255 MPa and 4.14%, respectively. The as-rolled UTS along TD reached 325 MPa, about 30% higher than that along the RD. After heat treatment, the anisotropy of mechanical properties remained. The microstructure evolution and mechanical properties were discussed in detail. Full article
Figures

Figure 1

Open AccessReview
Near Net Shape Manufacture of Titanium Alloy Components from Powder and Wire: A Review of State-of-the-Art Process Routes
Metals 2019, 9(6), 689; https://doi.org/10.3390/met9060689
Received: 20 May 2019 / Revised: 8 June 2019 / Accepted: 13 June 2019 / Published: 15 June 2019
Viewed by 803 | PDF Full-text (11471 KB) | HTML Full-text | XML Full-text
Abstract
Near net shape (NNS) manufacturing offers an alternative to conventional processes for the manufacture of titanium alloy components. Compared to the conventional routes, which typically require extensive material removal of forged billets, NNS methods offer more efficient material usage and can significantly reduce [...] Read more.
Near net shape (NNS) manufacturing offers an alternative to conventional processes for the manufacture of titanium alloy components. Compared to the conventional routes, which typically require extensive material removal of forged billets, NNS methods offer more efficient material usage and can significantly reduce machining requirements. Furthermore, NNS manufacturing processes offer benefits such as greater flexibility and reduced costs compared to conventional methods. Processes such as metal additive manufacturing (AM) have started to be adopted in niche applications, most notably for the manufacture of medical implants, where many conventionally forged components have been replaced by those manufactured by AM processes. However, for more widespread adoption of these emerging processes, an improvement in the confidence in the techniques by manufacturers is necessary. This requires addressing challenges such as the limited mechanical properties of parts in their as-built condition compared to wrought products and the post-process machining requirements of components manufactured by these routes. In this review, processes which use a powder or wire feedstock are evaluated to assess their capabilities for the manufacture of titanium alloy components. These processes include powder bed fusion and direct energy deposition metal additive processes as well as hybrid routes, which combine powder metallurgy with thermomechanical post-processing. Full article
(This article belongs to the Special Issue Powder Metallurgy of Titanium Alloys )
Figures

Figure 1

Open AccessArticle
Three-Dimensional (3D) Microstructure-Based Modeling of a Thermally-Aged Cast Duplex Stainless Steel Based on X-ray Microtomography, Nanoindentation and Micropillar Compression
Metals 2019, 9(6), 688; https://doi.org/10.3390/met9060688
Received: 1 May 2019 / Revised: 7 June 2019 / Accepted: 13 June 2019 / Published: 15 June 2019
Viewed by 519 | PDF Full-text (4731 KB) | HTML Full-text | XML Full-text
Abstract
Finite element analysis was conducted on a thermally-aged cast duplex stainless steel based on the true three-dimensional (3D) microstructure obtained from X-ray microtomography experiments and using the constitutive behavior of each individual phase extracted from nanoindentation on single-crystal and bicrystal micropillar compression tests. [...] Read more.
Finite element analysis was conducted on a thermally-aged cast duplex stainless steel based on the true three-dimensional (3D) microstructure obtained from X-ray microtomography experiments and using the constitutive behavior of each individual phase extracted from nanoindentation on single-crystal and bicrystal micropillar compression tests. The evolution of the phase morphology, the mechanical properties and the boundary deformation behavior during the aging process are highlighted. Quantitative analysis in terms of the distribution and evolution of the stress and strain in both the as received and aged conditions was performed. The experimental results show that aging at an intermediate temperature has a negligible influence on the morphology of the two phases in cast duplex stainless steel (CDSS). Results from simulations reveal that the mechanical behavior of this material were seriously affected by the microstructure and the mechanical properties of the individual phase and the necking deformation tend to form in the area with less large ferrite grains after aging. In addition, stress localization tends to form at the austenite/ferrite interface, in the narrow region of ferrite grains and in the small ferrite grains. Full article
Figures

Figure 1

Open AccessArticle
An Investigation of Non-Metallic Inclusions in Different Ferroalloys using Electrolytic Extraction
Metals 2019, 9(6), 687; https://doi.org/10.3390/met9060687
Received: 16 May 2019 / Revised: 31 May 2019 / Accepted: 11 June 2019 / Published: 15 June 2019
Viewed by 518 | PDF Full-text (8722 KB) | HTML Full-text | XML Full-text
Abstract
Ferroalloys are integral constituents of the steelmaking process, since non-metallic inclusions (NMIs) from ferroalloys significantly influence the transformation of inclusions present in liquid steel or they are directly involved in casted steel. In this study, the characteristics of inclusions (such as the number, [...] Read more.
Ferroalloys are integral constituents of the steelmaking process, since non-metallic inclusions (NMIs) from ferroalloys significantly influence the transformation of inclusions present in liquid steel or they are directly involved in casted steel. In this study, the characteristics of inclusions (such as the number, morphology, size, and composition) in different industrial ferroalloys (FeV, FeMo, FeB, and FeCr) were investigated using the electrolytic extraction (EE) technique. After extraction from the ferroalloy samples and filtration of the solution, the inclusions were investigated on a film filter. The three-dimensional (3D) investigations were conducted using a scanning electron microscopy in combination with energy dispersive spectroscopy (SEM-EDS). The characteristics of inclusions observed in the ferroalloys were compared with previous results and discussed with respect to their possible behaviors in the melt and their effects on the quality of the cast steels. The particle size distributions and floatation distances were plotted for the main inclusion types. The results showed that the most harmful inclusions in the ferroalloys investigated are the following: pure Al2O3 and high Al2O3-containing inclusions in FeV alloys; pure SiO2 and high SiO2-containing inclusions in FeMo alloys; Al2O3 and SiO2-containing inclusions in FeB alloys; and MnO-Cr2O3, Al2O3, and Cr2O3-based inclusions in FeCr alloys. Full article
(This article belongs to the Special Issue Inclusion/Precipitate Engineering in Steels)
Figures

Figure 1

Metals EISSN 2075-4701 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top