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3 pages, 154 KiB

Open AccessEditorial

Alloy and Process Design of Metallic Materials

by Mohamed Soliman

Metals 2023, 13(10), 1788; https://doi.org/10.3390/met13101788 - 23 Oct 2023

Viewed by 1393

Abstract

Metallic materials have witnessed substantial developments over the past two decades [...] Full article

(This article belongs to the Special Issue Alloy and Process Design of Metallic Materials)

Research

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16 pages, 9648 KiB

Open AccessArticle

On the Microstructure Development under Cyclic Temperature Conditions during WAAM of Microalloyed Steels

by Chang Huang, Mohamed Soliman, Kai Treutler, Volker Wesling and Karl-Heinz Spitzer

Metals 2022, 12(11), 1913; https://doi.org/10.3390/met12111913 - 8 Nov 2022

Cited by 6 | Viewed by 1454

Abstract

This paper shed light on the kinetics of transformation and the developed microstructure during wire arc additive manufacturing (WAAM). Three microalloyed alloys, two of them are high strength low alloyed steel (HSLA) grades and the third is a Ni-Cr-Mo steel, from which the [...] Read more.

This paper shed light on the kinetics of transformation and the developed microstructure during wire arc additive manufacturing (WAAM). Three microalloyed alloys, two of them are high strength low alloyed steel (HSLA) grades and the third is a Ni-Cr-Mo steel, from which the welding wires are being produced, were investigated. Repeated cycles around varied temperatures from a reheating temperature of 1350 °C and down to a temperature 35 °C below the A_e1 are applied using dilatometer on samples from the steels. After applying the cycles, the dilatometric-samples were investigated metallographically and their macro- and microhardness values were measured. It is shown that the WAAM using HSLA steels produce softer structure than the steel of the welding wire. Combined microalloying with Ti and Nb can present a useful strategy for producing finer structure in the WAAM components due to the effect of Ti in inhibiting the prior austenite grain-growth and that of Nb in refining the final structure. Additionally, repeated heating near A_e3 refines the prior austenite grains and produced fine ferrite-pearlite structure in case of HSLA steels and a microstructure predominated by the granular bainite in case of welding wire alloy. The former microstructure was the softest one for the case of HSLA steels, whereas the softest structure in case of the welding wire alloy was the tempered martensite structure developed by reheating below A_e1. Idealized temperature curves were chosen for the heat treatment, which could be characterized in a well-defined manner. In future work such idealized curves together with temperature histories obtained in WAAM-process will be used to set up a database to train an AI-model for predicting structure and material properties. Full article

(This article belongs to the Special Issue Alloy and Process Design of Metallic Materials)

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21 pages, 140936 KiB

Open AccessArticle

Processing Route Optimization and Characterization of Al6063–SiCp Metal-Matrix Composite Sheets

by Mohamed Soliman, Mohamad Akram, Michael Dawoud, Ahmed Elsabbagh, Mohamed A. Taha and Heinz Palkowski

Metals 2022, 12(4), 536; https://doi.org/10.3390/met12040536 - 22 Mar 2022

Cited by 2 | Viewed by 1884

Abstract

The target of this study is to develop routes for processing Al–SiCp (SiC particulate) sheets with improved microstructures; namely, the uniform distribution of SiCp and minimized porosity throughout the whole material, thereby improving its mechanical properties. Al–SiCp composites reinforced with 5, 10, and [...] Read more.

The target of this study is to develop routes for processing Al–SiCp (SiC particulate) sheets with improved microstructures; namely, the uniform distribution of SiCp and minimized porosity throughout the whole material, thereby improving its mechanical properties. Al–SiCp composites reinforced with 5, 10, and 15 vol.% SiC and having three average sizes of 29, 17, and 8.5 µm were produced using a semi-automated stir-casting machine; finally, the bars were hot rolled to get the final sheet dimensions. The rolling steps were performed based on the results of thermomechanical simulations performed on the cast blocks. The first rolling steps were applied according to a safe rolling schedule to avoid cracking via encouraging dynamic recrystallization. The last rolling steps were performed to improve the hardness and strength of the metal matrix composites (MMCs). A refinement in grain size from an average of 420 µm in the as-cast condition to an average of about 85 µm after rolling was observed. Some heterogeneity in grain size was observed where the regions with larger, elongated grains were associated with the zones depleted by SiCp reinforcement. Reinforcing with SiCp led to a small increase in tensile strength of 10–20 MPa, and this was further improved to about 60 MPa and 110 MPa for the 5 and 10 vol.% SiCp conditions, respectively, after a T6 heat treatment. Full article

(This article belongs to the Special Issue Alloy and Process Design of Metallic Materials)

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15 pages, 2754 KiB

Open AccessEditor’s ChoiceArticle

Influence of Quenching and Partitioning Parameters on Phase Transformations and Mechanical Properties of Medium Manganese Steel for Press-Hardening Application

by Charline Blankart, Sebastian Wesselmecking and Ulrich Krupp

Metals 2021, 11(11), 1879; https://doi.org/10.3390/met11111879 - 22 Nov 2021

Cited by 9 | Viewed by 2601

Abstract

It has been proven that through targeted quenching and partitioning (Q & P), medium manganese steels can exhibit excellent mechanical properties combining very high strength and ductility. In order to apply the potential of these steels in industrial press hardening and to avoid [...] Read more.

It has been proven that through targeted quenching and partitioning (Q & P), medium manganese steels can exhibit excellent mechanical properties combining very high strength and ductility. In order to apply the potential of these steels in industrial press hardening and to avoid high scrap rates, it is of utmost importance to determine a robust process window for Q & P. Hence, an intensive study of dilatometry experiments was carried out to identify the influence of quenching temperature (T_Q) and partitioning time (t_p) on phase transformations, phase stabilities, and the mechanical properties of a lean medium manganese steel. For this purpose, additional scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and energy dispersive X-ray spectroscopy (EDX) examinations as well as tensile testing were performed. Based on the dilatometry data, an adjustment of the Koistinen–Marburger (K-M) equation for medium manganese steel was developed. The results show that a retained austenite content of 12–21% in combination with a low-phase fraction of untempered secondary martensite (max. 20%) leads to excellent mechanical properties with a tensile strength higher than 1500 MPa and a total elongation of 18%, whereas an exceeding secondary martensite phase fraction results in brittle failure. The optimum retained austenite content was adjusted for T_Q between 130 °C and 150 °C by means of an adapted partitioning. Full article

(This article belongs to the Special Issue Alloy and Process Design of Metallic Materials)

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16 pages, 7650 KiB

Open AccessArticle

On the Impact of the Intermetallic Fe₂Nb Laves Phase on the Mechanical Properties of Fe-6 Al-1.25 Nb-X W/Mo Fully Ferritic Light-Weight Steels

by Robin Emmrich and Ulrich Krupp

Metals 2021, 11(11), 1693; https://doi.org/10.3390/met11111693 - 24 Oct 2021

Cited by 2 | Viewed by 1753

Abstract

The present study aims at the development of precipitation hardening fully ferritic steels with increased aluminum and niobium content for application at elevated temperatures. The first and second material batch were alloyed with tungsten or molybdenum, respectively. To analyze the influence of these [...] Read more.

The present study aims at the development of precipitation hardening fully ferritic steels with increased aluminum and niobium content for application at elevated temperatures. The first and second material batch were alloyed with tungsten or molybdenum, respectively. To analyze the influence of these elements on the thermally induced precipitation of the intermetallic Fe₂Nb Laves phase and thus on the mechanical properties, aging treatments with varying temperature and holding time are performed followed by X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) including elemental contrast based particle analysis as well as hardness measurements and tensile tests at room temperature and at 500 °C. The incorporation of molybdenum into the Laves phase sets in at an earlier stage of aging than the incorporation of tungsten, which leads to faster growth and coarsening of the Laves phase in the molybdenum-alloyed steel. Nevertheless, both concepts show a fast and massive increase in hardness (280 HV10) due to precipitation of Laves phase during aging at 650 °C. After 4 h aging, the yield strength increase at room temperature is 100 MPa, which stays stable at operation temperatures up to 500 °C. Full article

(This article belongs to the Special Issue Alloy and Process Design of Metallic Materials)

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20 pages, 13799 KiB

Open AccessFeature PaperArticle

Nano-Bainitic Steels: Acceleration of Transformation by High Aluminum Addition and Its Effect on Their Mechanical Properties

by Mohamad Akram, Mohamed Soliman and Heinz Palkowski

Metals 2021, 11(8), 1210; https://doi.org/10.3390/met11081210 - 29 Jul 2021

Cited by 4 | Viewed by 1774

Abstract

Additions of 3 and 5 wt.% Al have been investigated as a low-cost method for transformation acceleration in nano-bainitic steels. For both Al contents, two groups of steels with C-content in the range ~0.7 to ~0.95 wt.% were studied. Thermodynamic and physical simulations [...] Read more.

Additions of 3 and 5 wt.% Al have been investigated as a low-cost method for transformation acceleration in nano-bainitic steels. For both Al contents, two groups of steels with C-content in the range ~0.7 to ~0.95 wt.% were studied. Thermodynamic and physical simulations were used in alloy and heat treatment design. Characterization was performed via dilatometry, scanning and transmission electron microscopy, Synchrotron X-ray diffraction, and tensile and impact testing. Fast bainitic-transformation time-intervals ranging from 750–4600 s were recorded and tensile strengths up to 2000 MPa at a ductility of ~10 elongation percent were attainable for the 3 wt.% Al group at an austempering temperature of 265 °C. Higher Al additions were found to perform better than their lower Al counterparts as the austempering temperature is dropped. However, Al lowered the austenite stability, increased the martensite start temperature, austenitization temperatures and, consequently, the prior austenite grain size, as well as limiting the austempering temperatures to higher ones. Additionally, the lowered austenite stability coupled with higher additions of hardenability elements (here carbon) to maintain the martensite start at around 300 °C, causing the 5 wt.% Al group to have a large amount of low stability retained austenite (and consequently brittle martensite) in their microstructure, leading to a low elongation of around 5%. Full article

(This article belongs to the Special Issue Alloy and Process Design of Metallic Materials)

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17 pages, 5458 KiB

Open AccessArticle

Aging Behavior of Intercritically Quenched Ductile Iron

by Ali Abdelmonem, Mohamed Soliman, Heinz Palkowski and Ahmed Elsabbagh

Metals 2021, 11(6), 897; https://doi.org/10.3390/met11060897 - 31 May 2021

Cited by 1 | Viewed by 2212

Abstract

Although extensive aging and strain aging (bake hardening, BH) studies have been carried out on dual-phase steels, the aging behavior of the dual matrix structure (DMS) ductile iron (DI), as a potential way to improve its mechanical properties, has not been addressed until [...] Read more.

Although extensive aging and strain aging (bake hardening, BH) studies have been carried out on dual-phase steels, the aging behavior of the dual matrix structure (DMS) ductile iron (DI), as a potential way to improve its mechanical properties, has not been addressed until now. This research was designed to study the aging behavior of DI with a ferrite-martensite matrix structure. DMS-DI with a martensite volume fraction of 30% was produced by intercritical austenitizing at 785 °C followed by quenching in water to room temperature. Aging treatments were carried out without pre-straining at aging temperatures of 140, 170, and 220 °C for 2–10,000 min. DMS-DI was investigated by light optical microscopy (LOM) for unaged samples and scanning electron microscopy (SEM) for selected samples after aging treatments. The effect of aging conditions on the mechanical properties were investigated. Microhardness measurements for ferrite and martensite were also examined as a function of aging conditions. The increase in yield strength due to aging was determined. The results indicate that the aging conditions have a small effect on the ultimate tensile strength UTS. It is shown that the yield strength increased to a maximum value of 45 MPa (~11% increase) after aging for particular time, which is found to be dependent on the aging temperature. The peak aging response is followed by a decrease in yield strength, which is observed to be attributed to martensite tempering as confirmed by microhardness measurements. Full article

(This article belongs to the Special Issue Alloy and Process Design of Metallic Materials)

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22 pages, 12066 KiB

Open AccessArticle

Effect of Niobium on the Microstructure and Mechanical Properties of Alloyed Ductile Irons and Austempered Ductile Irons

by Mostafa Ahmed, Mohamed Soliman, Mervat Youssef, Rüdiger Bähr and Adel Nofal

Metals 2021, 11(5), 703; https://doi.org/10.3390/met11050703 - 25 Apr 2021

Cited by 10 | Viewed by 3379

Abstract

In this research, different ductile irons and austempered ductile irons were successfully developed using several alloying contents of nickel, copper and microalloying with niobium. Additionally, special nanocarbon powder was added to the molten iron to enhance the nucleation tendency of spheroidal graphite and [...] Read more.

In this research, different ductile irons and austempered ductile irons were successfully developed using several alloying contents of nickel, copper and microalloying with niobium. Additionally, special nanocarbon powder was added to the molten iron to enhance the nucleation tendency of spheroidal graphite and compensate for the possible negative effect of Nb addition on the nodule morphology. Metallographic analysis showed that increasing the niobium content in the alloy to 0.1 wt % raises the number of graphite eutectic cells and refines the final structure of the graphite. Moreover, the nodule count of graphite slightly increased, but it concurrently decreased the nodularity when the Nb amount reached 0.1 wt %. SEM micrographs illustrated that nano- to microsized niobium carbides (NbC) particles were dispersed in the matrix of the Nb microalloyed ductile irons. Both optical and SEM micrographs clearly showed that alloying of ductile irons with nickel, copper and microalloying with niobium had a significant effect on defining the final pearlite structure. Coarse, fine, broken and spheroidized pearlite structures were simultaneously observed in all investigated alloys. Dilatometry studies demonstrated that the nano NbC particles acted as nucleation sites for graphite and ferrite needles. Therefore, Nb addition accelerated the formation of ausferrite during the austempering stage. Finally, alloying with Cu, Ni and microalloying with Nb led to developing novel grades of ADI with excellent strength/ductility property combination. Full article

(This article belongs to the Special Issue Alloy and Process Design of Metallic Materials)

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17 pages, 9536 KiB

Open AccessArticle

Microstructure and Mechanical Properties of V-Alloyed Rebars Subjected to Tempcore Process

by Essam Ahmed, Samir Ibrahim, Mohamed Galal, Sarah A. Elnekhaily and Tarek Allam

Metals 2021, 11(2), 246; https://doi.org/10.3390/met11020246 - 2 Feb 2021

Cited by 8 | Viewed by 3290

Abstract

Two B400B-R and B500B grade rebars were industrially produced through a Tempcore process. The standard chemical composition of B500B grade was additionally alloyed with 0.067 wt.% V to enhance its mechanical properties. A set of optimized processing parameters were applied to manufacture two [...] Read more.

Two B400B-R and B500B grade rebars were industrially produced through a Tempcore process. The standard chemical composition of B500B grade was additionally alloyed with 0.067 wt.% V to enhance its mechanical properties. A set of optimized processing parameters were applied to manufacture two different diameters D20 (Ø 20 mm) and D32 (Ø 32 mm). The microstructure -mechanical properties relationships were evaluated using optical and scanning electron microscopes, hardness, and tensile testing. In addition, a thermal model was developed to define the thermal cycle evolution during cooling in the quenching & tempering box (QTB) to simulate the kinetics of V(C,N) precipitation. The microstructure observations showed a typical graded microstructure consisting of ferrite-pearlite core and outer tempered martensite ring for both grades of both diameters. The optimized processing parameters for B400B-R of D32 (compared with D20) resulted in softening of the core (from 160 to 135 HV10) and tempered martensite surface (from 220 to 200 HV10) as well as in decreasing the yield strength (from 455 to 413 MPa) and tensile strength (from 580 to 559 MPa). On the contrary, an increase in hardness of the core (from 165 to 175 HV10) and the outer tempered martensite (from 240 to 270 HV10), in addition to an increase in yield strength (from 510 to 537 MPa) at almost the same level of tensile strength of 624–626 MPa are observed for B500B grade D32 compared with D20. The modeling and simulation calculations suggest that the manufacturing D32 rebars of B500B grade involves longer quenching time in the QTB which allow deeper tempered martensite surface along with a relatively higher core temperature that renders faster kinetics and larger volume fraction of V(C,N) precipitates. The current study demonstrates that the full potential of V-alloying can be exploited when a sufficient quenching time at the equalization temperature is achieved, which is valid for D32 rebars. Full article

(This article belongs to the Special Issue Alloy and Process Design of Metallic Materials)

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13 pages, 3423 KiB

Open AccessArticle

The Influence of Cooling Rate on Microstructure and Mechanical Properties of AlSi9Cu3

by Matic Žbontar, Mitja Petrič and Primož Mrvar

Metals 2021, 11(2), 186; https://doi.org/10.3390/met11020186 - 21 Jan 2021

Cited by 15 | Viewed by 3372

Abstract

The aim of this study was to determine the correlation between the size and the distribution of microstructural constituents and their cooling rate, as well as the correlation between the mechanical properties and the cooling rate of AlSi9Cu3 aluminum alloy when cast in [...] Read more.

The aim of this study was to determine the correlation between the size and the distribution of microstructural constituents and their cooling rate, as well as the correlation between the mechanical properties and the cooling rate of AlSi9Cu3 aluminum alloy when cast in high-pressure die casting (HPDC) conditions. In other words, the ultimate goal of the research was to determine the mechanical properties for a casting at different cooling rates. Castings with different wall thicknesses were chosen, and different cooling rates were assumed for each one. Castings from industrial technological practice were systematically chosen, and probes were extracted from those castings for the characterization of their mechanical properties. Special non-standard cylinders were created on which compressive tests were carried out. The uniqueness of this research lies in the fact that the diameters of the designed cylinders were in direct correlation to the actual wall thickness of the castings. This is important because the solidification of metal in the die cavity is complex, in that the cooling rates are higher on the surface of the casting than in the center. Local in-casting cooling rates were determined using numerical simulations. It was discovered that with increasing cooling rates from 60 K/s to 125 K/s the values for strength at 5% deformation increased on average from 261 MPa to 335 MPa. Full article

(This article belongs to the Special Issue Alloy and Process Design of Metallic Materials)

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22 pages, 10969 KiB

Open AccessArticle

Microstructural Control and Properties Optimization of Microalloyed Pipeline Steel

by Mohamed Soliman

Metals 2020, 10(11), 1499; https://doi.org/10.3390/met10111499 - 10 Nov 2020

Cited by 6 | Viewed by 1690

Abstract

A series of physical simulations, with parameters resembling those of industrial rolling, were applied using a thermo-mechanical simulator on microalloyed bainitic pipeline steel to study the influence of varying the processing parameters on its microstructure evolution and mechanical properties. In this study, the [...] Read more.

A series of physical simulations, with parameters resembling those of industrial rolling, were applied using a thermo-mechanical simulator on microalloyed bainitic pipeline steel to study the influence of varying the processing parameters on its microstructure evolution and mechanical properties. In this study, the austenitization temperature and roughing parameters were kept unchanged, whereas the parameters of the finishing stage were varied. The developed microstructures were studied using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is illustrated that selecting the appropriate cooling strategy (without altering the deformation schedule) can produce an optimized microstructure that breaks through the strength–ductility trade-off. Increasing the cooling rate after the finishing stage from 10 K·s⁻¹ to 20 K·s⁻¹ activated the microstructure refinement by effective nucleation of acicular ferrite and formation of finer and more dispersed martensite/austenite phase. This resulted in a remarkable enhancement in the ductility without compensating the strength. Furthermore, a pronounced strength increase with a slight ductility decrease was observed when selecting the appropriate coiling temperature, which is attributed to the copious precipitation associated with locating the coiling temperature near the peak temperature of precipitation. On the other hand, it was observed that the coiling temperature is the predominant parameter affecting the strain aging potential of the studied steel. Higher strain aging potentials were perceived in the samples with lower yield strength and vice versa, so that the differences in yield strength after thermo-mechanical treatments evened out after strain aging. Full article

(This article belongs to the Special Issue Alloy and Process Design of Metallic Materials)

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