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Corrosion is an inevitable and persistent issue that affects various metallic infrastructures, leading to significant economic losses and safety concerns, particularly in areas near or in contact with saline solutions such as seawater. Green corrosion inhibitors are compounds derived from natural sources that are biodegradable in various environments, offering a promising alternative to their conventional counterparts. Despite their potential, green corrosion inhibitors still face several limitations and challenges when exposed to NaCl environments. This comprehensive review delves into these limitations and associated challenges, shedding light on the progress made in addressing these issues and potential future developments as tools in corrosion management. Explicitly the following aspects are covered: (1) attributes of corrosion inhibitors, (2) general corrosion mechanism, (3) mechanism of corrosion inhibition in NaCl, (4) typical electrochemical and surface characterization techniques, (5) theoretical simulations by Density Functional Theory, and (6) corrosion testing standards and general guidelines for corrosion inhibitor selection. This review is expected to advance the knowledge of green corrosion inhibitors and promote further research and applications. [ABSTRACT FROM AUTHOR]

Traditional metallic biomaterials including titanium and its alloys, stainless steel, cobalt‐chromium alloys, magnesium alloys are gold standards for load bearing hard tissue applications, because of adequate mechanical properties such as elastic modulus, ductility and strength for long term support and stability. However, metallic implants suffer from poor osteointegration and early degradation in host body, owing to an array of factors which include stress shieling effect, corrosion, metal toxicity, microbial contamination and low bioactivity. Therefore, to improve integration of implants with host tissue and overall mechanical and biological functions, metallic implants are coated with bioactive glasses (BG). BG are one of the most promising implant coating materials used for bone repair and reconstruction, mainly because of excellent angiogenic, osteoconductive, osteoinductive, corrosion resistance, resorbability, biocompatibility, bioactivity and anti‐microbial properties. Various BG compositions are employed for diverse biomedical applications ranging from wound healing, bone formation, corrosion resistance, drug delivery to scaffolds in tissue engineering and different methods are used for coating BG on implants to enhance stability and bond strength between implant and coating. This narrative review gives a detailed overview on metallic implants, issues of metal alloys when used in implants and how metallic implants are improved by various BG compositions and coating methods. This review provides an updated information on advantages of different BG compositions in implants fabrication in order to address challenges and tailor mechanical and biological properties of implants for future applications. [ABSTRACT FROM AUTHOR]

Al–Zn–Mg–Cu alloys have been prepared using the gravity die-casting process. The influence of copper addition on microstructure, mechanical and thermal properties are studied. The experimental alloys were prepared using 5754 alloys, Al–Cu alloys, and pure zinc (solid form). Alloys are mechanically stirred for uniform distributions of alloying elements and precipitate phases. Four alloys with different copper weight percentages (0.02 wt%, 0.89 wt%, 1.57 wt%, and 3.34 wt%) were prepared. The α-Al and η (MgZn2) phases are observed in as-cast Al–Zn–Mg alloy. The addition of copper in Al–Zn–Mg alloys formed a θ phase (Al2Cu). Micro-Vickers hardness of Al–Zn–Mg–Cu alloy increased (from 116 HV1 to 133 HV1) with copper addition (0.02–1.57 wt%) at firstly due to the formation of θ phase (Al2Cu). Then, micro-Vickers hardness decreases due to high amounts of precipitates. Copper addition reduces the melting point (623–612 °C) and precipitation temperature (472–466 °C) of aluminum alloy. Al–Zn–Mg alloys have tensile strength of 422 MPa due to precipitates phase formation of η and T phases, solid solution strengthening (zinc and magnesium). Copper addition increases tensile strength due to the formation of θ phases. After achieving a strength of 486 MPa at an elongation of 3.72% (1.57 wt% Cu), tensile strength reduces due to a higher amount of precipitates. [ABSTRACT FROM AUTHOR]

This paper presents the synthesis and characterization of Al-0.35Cu-0.18Sc-0.06Zr alloys, possessing remarkable electrical and mechanical properties. Specifically, the electrical conductivity and tensile strength of this alloy are reported to reach 60.4%IACS and 169.46 MPa, respectively. The electrical conductivity combined with Wiedemann–Franz law was calculated for Al-0.35Cu-0.18Sc-0.06Zr alloys thermal conductivity as showing excellent thermal conductivity. Microscopic analysis shows that a large number of fine "bean-petal" shaped Al3(Sc, Zr) particles, i.e., the second phase, were diffusely distributed in the alloy. These particles are highly cohered with the matrix, resulting in small and shallow toughness dimples at the tensile fracture. Due to the low diffusion coefficient of Zr element, the growth rate of precipitated second phase particles can be effectively reduced, which leads to forming Al3(Sc, Zr) phase with Zr-rich shell and improving the intrinsic coarsening property of Al3Sc phase. The Al3(Sc, Zr) second phase exhibits a large surrounding strain of approximately 2.5%, resulting in a significant elastic strain field that inhibits dislocation movement, thereby increasing alloy strength. Furthermore, the heat resistance test results show that the alloy can operate steadily at 503 K for up to 350, 400 h. [ABSTRACT FROM AUTHOR]

Inconel 718 has good fabricability, high strength at elevated temperatures, and high corrosion resistance and is widely deployed in many aerospace and other high-performance applications. With the molten pool's rapid solidification during laser powder bed fusion (LPBF), the resulting microstructures differ from those expected in equilibrium conditions. Residual stresses, microsegregation, anisotropy, undesirable phases, layered structure, and lower mechanical properties are the challenges that must be addressed before LPBF-ed Inconel 718 parts can be industrially implemented. Heat treatment of Inconel 718 after the LPBF process is widely discussed in the literature, and the proposed heat treatment processes do not address all the challenges mentioned above. For this reason, specific heat treatments should be designed to achieve desired mechanical properties. Four different high-temperature heat treatment procedures were developed and tested in recent work to study the effect of various heat treatment parameters on the type of precipitates, grain size, room and elevated temperature mechanical properties, and creep properties of LPBF-ed Inconel 718. Two heat treatment procedures were designed to study the effect of eliminating the stress relief cycle and increasing the soaking time of solution heat treatment at the same hot isostatic pressing (HIP) and aging conditions. The other two heat treatment procedures were designed to study the effect of stress relief and aging parameters, with similar HIP and solution annealing parameters. The investigated heat treatment procedures showed the formation of equiaxed grain size and a significant amount of γ″ particles at the grain boundary in addition to primary carbide types (MC). Three different grain sizes could be obtained, starting with the same as-built microstructure by controlling post-process heat treatment parameters. The first type, coarse grain size (ASTM grain size No. G 3), suitable for creep application, was achieved by increasing the soaking time at the aging cycle. The second type, the formation of serrated grain boundaries suitable for good fatigue and creep properties, was achieved by decreasing the stress relief cycle's soaking time and temperature. The third type, fine grain size (ASTM grain size No. G 6), which is preferable for fatigue properties, was achieved by decreasing the soaking time at the solution annealing cycle. Among the different heat treatment conditions, the heat treatment with lower stress relief temperature and longer soaking time at solution annealing steps showed compromised equiaxed grain size with serrated grain boundaries, and it was selected for mechanical testing. The mechanical properties at room and elevated temperature (650 °C) and creep properties under constant axial stress of 690 MPa at 650 °C until failure were evaluated. The obtained elongation is > 2 × higher than the available properties in the AMS 5663 for wrought Inconel 718, AMS 5383 for cast Inconel 718, and ASTM F3055 for LPBF while maintaining a higher tensile strength above the average level found in the standards. It can be concluded that the performed heat treatment achieves higher mechanical properties. The values of UTS, YS, elongation, and reduction of area percentages are similar in the Z and XY orientations, revealing the presence of isotropic microstructure and uniform distribution of MC and γ″ precipitates. [ABSTRACT FROM AUTHOR]

The study investigates the influence of ultrasound on the microstructure and properties of AlCoCrFeNi fabricated by laser cladding. The results indicate that the grain size of AlCoCrFeNi prepared by ultrasonic assistance is smaller than that prepared without ultrasound. Moreover, employing ultrasound in the fabrication process of AlCoCrFeNi results in an improvement in its electrochemical corrosion resistance. This enhancement can be attributed to the homogenization of the microstructure and the reduction of microgalvanic couples. The wear resistance of AlCoCrFeNi is enhanced with the increase in ultrasound amplitude. The sample prepared using a 15 μm ultrasonic amplitude demonstrates the lowest friction coefficient of 0.3876 and the minimal wear loss of 40.8 mg. The tensile strength and elongation of AlCoCrFeNi are improved as the ultrasonic amplitude increases. The sample prepared using a 15 μm ultrasonic amplitude demonstrates the highest tensile strength and elongation, measuring 1039 MPa and 16.2%, respectively. The enhancement of mechanical properties can be attributed primarily to the grain refinement and the reduction of as-cast defects.

Several ternary RareEarth-Magnesium-Nickel intermetallics (RE-Mg-Ni) emerged in last decade for their specific hydrogen storage capability. Nickel is now considered among strategic metals with recurrent rising price, Magnesium although its good gravimetric facility suffers from frequent oxidation or irreversible poisoning. Zirconium alloys are recognized for their improved anti-corrosion properties with enhanced wear resistance for high temperature machinability in industrial applications or energy research purposes. We proposed in this paper double substitution possibility replacing Magnesium and reducing Nickel charge. We developed new generation of quaternary Zirconium-AB3 intermetallic LaZr2Ni5Al4 using mechanical alloying method. Two binary raw materials are involved in this alloying reaction, the first is LaNi5 and the second is ZrAl2 (Laves phase C14) and both precursors are achieved quasi-quantitively using high frequency induction melting. The final target AB3 compound crystallizes in Trigonal system with space group R-3m (166) and following experimental conditions (Fritsch P7, Ω = 450 rpm) an acceptable synthesis yield (>80%) is obtained starting from 20 hours mechanical alloying. Rietveld refinement is performed to have real matrix parameters and AB3 powder surface is analyzed using Scanning Electron Microscopy.

An elongation of 880 % was obtained at a high initial strain rate of 1 × 10−2 s−1 at 470 °C in an Al–Cu–Li alloy produced by traditional thermomechanical-processing. The high-strain-rate superplastic deformation mechanisms during the whole deformation process were studied by SEM, EBSD, and FIB techniques. High-resolution surface studies employing focused ion beams reveal that grain boundary sliding accounts for up to 70 % of the overall strain. Furthermore, this phenomenon consistently maintains a high level, with a minimum value of 56 %, throughout the entire deformation process. Meanwhile, diffusion creep plays an accommodating role and stimulates the formation of striated bands.

• Life Cycle Analysis of two materials for spacecraft structures is conducted. • A relationship between fragments generation and materials properties is established. • A novel metric for the evaluation of debris generation upon collision is introduced. • Results are discussed based on terrestrial and orbital impact indicators. Space debris are a primary environmental concern for the sustainability of space mission activities. When considering terrestrial applications, the Life Cycle Assessment represents a widely standardised technique for estimating the environmental impacts of human activities; however, its implementation in the space-related value chain is still in an early stage. In this study, the implications of two alternative materials in the development of a CubeSat structural bus are investigated with reference to the well-established categories for the Life Cycle Impact Assessment. Moreover, the potential impact of these materials on the orbital environment is quantified by the evaluation of the number of generated fragments upon collision for different significant low Earth orbits. The results of this study allow to quantify the impact of alternative design solutions for space systems on the terrestrial environment as well as the degradation of the orbital resources as a result of the space debris generation. [ABSTRACT FROM AUTHOR]

Several ternary RareEarth-Magnesium-Nickel intermetallics (RE-Mg-Ni) emerged in last decade for their specific hydrogen storage capability. Nickel is now considered among strategic metals with recurrent rising price, Magnesium although its good gravimetric facility suffers from frequent oxidation or irreversible poisoning. Zirconium alloys are recognized for their improved anti-corrosion properties with enhanced wear resistance for high temperature machinability in industrial applications or energy research purposes. We proposed in this paper double substitution possibility replacing Magnesium and reducing Nickel charge. We developed new generation of quaternary Zirconium-AB3 intermetallic LaZr2Ni5Al4 using mechanical alloying method. Two binary raw materials are involved in this alloying reaction, the first is LaNi5 and the second is ZrAl2 (Laves phase C14) and both precursors are achieved quasi-quantitively using high frequency induction melting. The final target AB3 compound crystallizes in Trigonal system with space group R-3m (166) and following experimental conditions (Fritsch P7, Ω = 450 rpm) an acceptable synthesis yield (>80%) is obtained starting from 20 hours mechanical alloying. Rietveld refinement is performed to have real matrix parameters and AB3 powder surface is analyzed using Scanning Electron Microscopy. [ABSTRACT FROM AUTHOR]

This study investigates the impact of a high-entropy alloy filler metal coated with copper (Cu) and post-weld heat treatment (PWHT) on the weldability of a ferrous medium-entropy alloy (MEA) in gas tungsten arc welding. The addition of 1-at% Cu had an insignificant effect on the microstructural behaviour, despite a positive mixing enthalpy with other elements. It was observed that a small amount of Cu was insufficient to induce phase separation into the Cu-rich phase and refine the microstructure of the as-welded specimen. However, with an increase in the PWHT temperature, the tensile strength remained mostly consistent, while the elongation significantly increased (elongation of as welded, PWHT700, PWHT800, and PWHT 900 were 19, 43, 55 and 68%, respectively). Notably, the PWHT temperature of 900 °C yielded the most desirable results by shifting the fracture location from the coarse-grained heat-affected zone (CGHAZ) to base metal (BM). This was due to significant recrystallisation and homogenised hardness of the cold-rolled BM during PWHT. However, the CGHAZ with coarse grains induced by the welding heat input remained invariant during the PWHT. This study proposes a viable PHWT temperature (900 °C) for enhancing the weldability of cold-rolled ferrous MEA without additional process. [ABSTRACT FROM AUTHOR]

Manufacturing of steel and titanium-based bimetallic material using cold metal transfer-based wire arc additive manufacturing (CMT-WAAM) is a novel exploration. It can be helpful in on-line repairing of dissolver tank piping in nuclear reactor power plants. In the present work, owing to the unique characteristic of lower heat input, CMT-WAAM was used for fabrication of AISI 316L-Ti graded structure on the AISI 316L substrate. The deposition shows apparent cracks and delamination at the bimetallic interface. The interface microstructure mainly consists of Fe–Ti intermetallic compounds (IMCs) of cellular and dendritic shapes and their boundaries were wetted by Cr–Ti IMCs. However, the cellular grains were fine and equiaxed and there was no evidence of presence of large columnar grains. EDS results show that the total graded region was of approx. 6 mm and Fe shows deeper penetration into Ti due to lesser requirement of activation energy. The presence of brittle IMC phases was also confirmed by the XRD analysis. [ABSTRACT FROM AUTHOR]

Corrosion is an inevitable and persistent issue that affects various metallic infrastructures, leading to significant economic losses and safety concerns, particularly in areas near or in contact with saline solutions such as seawater. Green corrosion inhibitors are compounds derived from natural sources that are biodegradable in various environments, offering a promising alternative to their conventional counterparts. Despite their potential, green corrosion inhibitors still face several limitations and challenges when exposed to NaCl environments. This comprehensive review delves into these limitations and associated challenges, shedding light on the progress made in addressing these issues and potential future developments as tools in corrosion management. Explicitly the following aspects are covered: (1) attributes of corrosion inhibitors, (2) general corrosion mechanism, (3) mechanism of corrosion inhibition in NaCl, (4) typical electrochemical and surface characterization techniques, (5) theoretical simulations by Density Functional Theory, and (6) corrosion testing standards and general guidelines for corrosion inhibitor selection. This review is expected to advance the knowledge of green corrosion inhibitors and promote further research and applications.

Stable precipitate takes the essential role for material strengthening in Al–Mg–Si alloys. To reveal how the stable precipitate works in material strengthening, a molecular dynamics model is carried out to show the interaction between the edge dislocations and the plate‐shaped β phase of Mg2Si. The critical resolved shear stress (CRSS) is related to the precipitate characteristics including sizes and thickness directions. The CRSS increases with the increase of the precipitate size. When the thickness direction of precipitate changes from [001] to [100], the CRSS increases from 326.76 to 368.7 MPa. This phenomenon is mainly affected by the interaction length between dislocation and β phase. With the increase of interaction length, the interaction time for dislocation to overcome pinning increases. The critical bending angle of dislocation can be affected by the interaction time and shear strain rate. The relationship between the critical bending angle and the CRSS in Al–Mg–Si alloy is then established. [ABSTRACT FROM AUTHOR]

Metal additive manufacturing is a method of producing metallic parts layer-by-layer. Some drawbacks, including anisotropy in mechanical properties, detrimental residual stresses, and the presence of columnar grain structures can affect the quality and performance of additively manufactured metallic parts. Therefore, different industrial sectors have employed intuitive ancillary processes to improve the quality of additively manufactured parts. Of particular interest is in-situ ancillary processes that are more applicable than other procedures due to their utmost importance to reduce manufacturing cycle time. In this review article, after introducing various metal additive manufacturing technologies, some of the common alloys utilized in those processes were discussed. With an eye toward improving the quality of additively manufactured components, the focus of the review was then shifted toward the effects of building direction, processing parameters, and Alloying composition Modification on microstructure and mechanical properties. The efficacy of ancillary processes such as metalworking, in-situ heat treatment, and in-situ thermo hydrogen process in reducing defects and improving physical and mechanical properties was then presented. The interwoven effects of in-situ ancillary methods along with additive manufacturing process parameters on designing parts with optimum design for different alloys and systems. [ABSTRACT FROM AUTHOR]

Severe plastic deformation through the machining process is an alternative method to achieve better surface features and morphology. In this study, the impact of cutter terminology (Radial Rake Angle) and machining constraints under Minimum Quantity Lubrication condition (constant flow rate) on the XRD spectra and surface features such as hardness, compressive residual stress and wear rate of the slot milled samples has been examined and found that the cutter terminology has offered a greater impact on the surface modification process followed by the machining constraints, owing to the generation of greater strain toughening and thermal soothing effect during the slot milling process. Further, the worn surface morphological analysis has confirmed the enhancement in surface features. [ABSTRACT FROM AUTHOR]

Fe65Co35 based soft magnetic alloys (SMAs) have been gaining attention for their superior magnetic features and playing significant roles in composite permanent magnets, magnetic storage and automotive electrification technologies. In the present work, the Fe65Co35 alloy were produced by arc melting with subsequent annealing. The effects of arc melting and annealing upon the structural and magnetic properties of the soft magnetic phase of the alloy Fe65Co35 have been investigated. The variation in magnetic and microstructural characteristics with melting and annealing have been observed using the X-ray diffractometer (XRD), scanning electron microscope (SEM), and the vibrating sample magnetometer (VSM). The XRD patterns verified the existence of the Fe65Co35 alloy. After melting and annealing, the alloy surface morphologies were examined using SEM. In this approach, the Fe65Co35 alloy was annealed at 600 °C for 4 h in an argon environment which resulted in the highest saturation magnetization of 237 emu/g and the lowest coercivity of 31 Oe. The rise in saturation magnetization was attributed to the removal of impurities, during the melting and annealing process.

In this study, a novel heterogeneous double-wire arc additive manufacturing method was used for the in-situ synthesis of a novel Ti–Ni–Al–V alloy wall. The results indicated that the synthesis wall was composed of the NiTi2, B2, and Ni4Ti3 phases from the bottom to the top. With an increase in deposition layers, the Ti2Ni content decreased. The hardness at the bottom was ∼685.4 HV0.2, while that of the middle and stable regions was 553 HV0.2. The maximum compressive strength was 2100 MPa. The fracture morphology was brittle. After cyclic compression, the recoverable and unrecoverable strains were 4.79 % and 1.21 %, respectively, indicating excellent recovery characteristics. Highlights: • A novel Ti–Ni–Al–V alloy fabricated in situ for the first time • Reaction between pure Ni and Ti–6Al–4V wires occurs in weld pool • As-Built wall is composed of NiTi2, B2, and Ni4Ti3 phases • Microhardness of Ti–Ni–Al–V alloy stabilized at 553 HV0.2.

Medium entropy alloy (MEA) is a hot spot in the field of material research in recent years. At present, the most widely used processing method of MEAs is “casting-rolling-heat treatment”, and the preparation of CoCrNi MEA by laser additive manufacturing (LAM) is still in primary stage. In this study, CoCrNi MEAs were fabricated with different scanning speeds by laser additive manufacturing, and the influence of scanning speed on its mechanical properties was investigated. The results show that higher scanning speed can significantly improve the mechanical properties of CoCrNi MEA. Compared with the low-speed laser additive manufacturing (LSLAM) MEA, the tensile strength of high-speed laser additive manufacturing (HSLAM) MEA is increased by 5.6 % and the fracture strain is increased by 60 %, which is mainly due to the entanglement of 1/6 and 1/2 dislocations and the defect structure at the grain boundary. LAM is a promising technology that can promote the development and application of MEAs in industry.

Metal additive manufacturing (AM) technologies can be classified according to the physical process involving the raw material as fusion-based and solid-state processes. The latter includes sintering-based technologies, which are aligned with conventional fabrication techniques, such as metal injection molding (MIM), and take advantage of the freeform fabrication of the initial green part. In the present work, 17-4PH stainless steel samples were fabricated by material extrusion, or rather bound metal deposition (BMD), a solid-state AM technology. The powder-based raw material was characterized together with samples fabricated using different angular infill strategies. By coupling different characterization technologies, it was possible to identify and classify major properties and defects of the raw material and the fabricated samples. In addition, microstructural modifications were found to be linked with the mesostructural defects typical of the BMD solid-state additive manufacturing technology applied to metals. [ABSTRACT FROM AUTHOR]

Crack-free Cu alloy coating has been fabricated on Al alloy substrate with the existence of a Ag buffer layer. The Cu alloy coating had 12 at.% Al and 45 at.% Ag, which contributed to the formation of Cu solid solution and the eutectic phase (transformation temperature 780 °C). The eutectic phase was characterized as finer Cu solid solution and finer Ag solid solution. The Ag buffer layer had the main contents of Ag2Al and Ag solid solution, and it not only hindered the formation of brittle intermetallic compounds (IMCs)but also reduced the thermal stress as its intermediate coefficient of thermal expansion (CTE). Furthermore, the plastic deformation of Ag solid solution in the Ag buffer layer and Cu solid solution in Cu alloy coating also relieved the thermal stress which was generated during the cladding process. All these three aspects inhibited crack generation. And the hardness of the Cu alloy coating increased to approximately 275 HV due to the strengthening effect of Al solid solution, grain boundary within the finer eutectic phase, and nano twin in the Cu solid solution of the eutectic phase. [ABSTRACT FROM AUTHOR]

A multi-principal element alloy (MPEA) is a type of metallic alloy that is composed of multiple metallic elements, with each element making up a significant portion of the alloy. In this study, the initial atomic percentage of elements in an (AlFeNiTiVZr)1-xCrx MPEA alloy as a function of the position on the surface was investigated using machine learning algorithms. Given the absence of a linear relationship between the atomic percentage of elements and their location on the surface, it is not possible to discern any clear association from the dataset. To overcome this non-linear relationship, the prediction of the atomic percentage of elements was accomplished using both decision tree (DT) and random forest (RF) regression models. The models were compared, and the results were found to be consistent with the experimental findings (a coefficient of determination R2 of 0.98 is obtained with the DT algorithm and 0.99 with the RF one). This research demonstrates the potential of machine learning algorithms in the analysis of wavelength-dispersive X-ray spectroscopy (WDS) datasets.

Increasing service temperature of wrought Ni-based superalloy by increasing alloying degree and fraction of γ′ phase has come to a bottleneck. In present work, an attempt is made to make maximum use of carbide to strengthen Ni-based alloy with a simpler chemical composition. Multiple morphology characterization methods and high temperature tensile test show that the newly designed Ni(bal.)-20Cr-0.80C–12Ta (wt%) alloy can be strengthened by TaC and Cr-rich M7C3 carbide and shows good ductility at 800 °C. Phase transformation characteristics detected by differential scanning calorimetry (DSC) and high-temperature confocal laser scanning microscopy (CLSM) images shows that there is a potential for dispersive precipitation of carbide in the alloy to get better mechanical property.

We perform three-dimensional phase-field simulations of equiaxed solidification in Al–Cu thin samples. Purely diffusive conditions are considered in order to describe systems where convection and gravity effects can be neglected. The use of a parallel adaptive finite element algorithm introduced recently [Gong et al., Comput. Mater. Sci. 147 (2018) p. 338-352] allows us to reach the domain of copper concentrations used in practical applications ($c \ge 3$ wt% Cu). We compare the present results with those of a previous study which was restricted to lower copper concentrations ($c \le 2$ wt% Cu) [Boukellal et al., Materialia 1 (2018) p. 62-69] due to the use of a finite difference code. In the fast dendritic growth regime, our results confirm that the dimensionless growth length $\Lambda $ is independent of the copper concentration and the average separation distance between the dendrite nuclei. The new data obtained at higher copper concentrations lead to a more accurate estimate of $\Lambda $. Physical arguments are developed to specify the meaning of $\Lambda $ and the grounds of the scaling law $\Lambda =\mathrm{cst}$. Comparisons with available experimental results of the literature give additional support to this scaling law.

The relationship between the microstructure and the practical performance of two different copper-beryllium alloys including their lifetime has been investigated. Herein, two valves made of two different alloys with very similar compositions and the same heat treatment methods were investigated by various standard techniques including metallography, X-ray diffraction, chemical composition, microhardness, and thermal conductivity measurements. Although both alloys experienced the same heat-treatment processes, they revealed different thermal and mechanical properties due to the minor difference in their chemical composition. The alloy providing a longer lifetime (40% more) as the tip had a higher thermal conductivity of 280.3 W (m·K)−1 (about two times that of the other alloy). Regarding the metallography images and the measured thermal conductivity values of the alloys, the extended lifetime of the nozzle with the optimum performance is ascribed to its biphasic microstructure and the minor grain boundaries and interfacial thermal resistance. And important difference in the chemical composition was investigated in this study. [ABSTRACT FROM AUTHOR]

Flexible control of atomization pressure and bar material feeding speed was achieved during preparation of TC11 alloy 3D-printing spherical powder on basis of a vacuum-induced multistage atomization process. Collision at the metal drop atomization stage was effectively avoided and spherical powder quality was significantly enhanced while ensuring the high fine-powder yield. Under the optimized atomization process conditions, the powder with D90 of 59.2 μm, highest sphericity, O and N element increment below 0.04%, and 15–53 μm powder yield of 30% was obtained. These comprehensive mechanical properties meet the requirement for 3D printing.

A multi-principal element alloy (MPEA) is a type of metallic alloy that is composed of multiple metallic elements, with each element making up a significant portion of the alloy. In this study, the initial atomic percentage of elements in an (AlFeNiTiVZr)1-xCrx MPEA alloy as a function of the position on the surface was investigated using machine learning algorithms. Given the absence of a linear relationship between the atomic percentage of elements and their location on the surface, it is not possible to discern any clear association from the dataset. To overcome this non-linear relationship, the prediction of the atomic percentage of elements was accomplished using both decision tree (DT) and random forest (RF) regression models. The models were compared, and the results were found to be consistent with the experimental findings (a coefficient of determination R2 of 0.98 is obtained with the DT algorithm and 0.99 with the RF one). This research demonstrates the potential of machine learning algorithms in the analysis of wavelength-dispersive X-ray spectroscopy (WDS) datasets. [ABSTRACT FROM AUTHOR]

The deformation behavior of three tensile deformed high-Mn steels with varying Al contents (0, 1 and 3 wt.%) is discriminated on the basis of their respective critical shear stress of twinning, derived from their respective stacking fault energies (18.1-41.6 mJ/m2) estimated according to x-ray diffraction line profile analyses. The Al-free steel manifested maximum strain hardening rate ~ 3 GPa that gradually dropped with addition of Al. The critical twinning stress, τ c , of the steels was estimated as: 246, 348 and 561 MPa. Increasing stacking fault energies lead to an adaptation in deformation mechanism from: (γ → ε) transformation → deformation twinning → dislocation plasticity—as was noted from x-ray diffraction and transmission electron microscopy studies. The highest strain hardening observed in Al-free steel was attributed to the presence of ε -martensite in the austenite microstructure. The incidences of ε -martensite and/or twinning were found to be directly related to the equilibrium width of the overlapping stacking faults. The critical shear stress-based calculations could better explain the adaptation of plasticity mechanisms in Fe-Mn-Al-C steels than the prediction based on the stacking fault energy alone. [ABSTRACT FROM AUTHOR]

This paper presents a detailed study on the dimensional accuracy of Ti6Al4V parts manufactured by the wire feed laser directed energy deposition process as compared to the design data before any postprocessing, as the majority of the reported research is focused on the mechanical and microstructural properties of the manufactured parts. Due to the large layer thickness (1.2 mm) and high material deposition rate (15 mm/s), smaller rectangular samples were susceptible to more dimensional inaccuracies. Most of the samples have larger dimensions than the design data, which is favorable for postprocessing. Special consideration should be given to the Z axis as the top layer has the most curves on the periphery of the samples due to shrinkage upon cooling. Depositing the material along the periphery of the present layer at the start of each layer minimized the overflow of the molten alloy when the laser is near the edges of the model in each layer. Upon further inspection using an optical microscope and scanning electron microscope analysis, surfaces voids were observed. Only ∼0.5 mm was required to remove from each side to obtain a minimal crack-free flat surface. The microhardness of the samples ranged from 313.64 to 346.17 HV. [ABSTRACT FROM AUTHOR]

In this study, single pass rolling (SPR) with varied rolling reductions was conducted on pre-homogenized AZ91 alloys (H alloys) and ECAP-processed AZ91 alloys (HE alloys). The effects of rolling reduction on the microstructures and mechanical properties of HR alloys (pre-homogenized and rolled) and HER alloys (ECAP-processed and rolled) were investigated. The results showed that the HER alloys possessed much finer microstructures and superior mechanical properties than the HR alloys, which were significantly influenced by the rolling reduction. The microstructures of the HER alloys became bimodal, and the strength and elongation markedly improved with the increase in the rolling reduction. When the rolling reduction reached 70%, the HER alloys acquired a typical bimodal structure, contributing to their excellent comprehensive mechanical properties. [ABSTRACT FROM AUTHOR]

Weight reduction is often considered the primary goal in the development of structure materials. A new Ti-8Al-1Cr-1V-0.5Fe-0.1Si (wt.%) alloy with a low-density and a high-strength was developed in this work. The microstructures and mechanical properties of the alloy were investigated in hot-rolled and solution-aging (STA) treatment conditions. The microstructures of the alloy in both states consist of the spherical αp phase, acicular αs phase, and a small amount of β phase. Attributed to such heterogeneous microstructures, the hot-rolled alloy exhibits an outstanding tensile strength of 1046.1 MPa, a total elongation of ~8.3%, and an impressive low density of 4.23 g/cm3. After heat treatment, the alloy also exhibits a similar strength and ductility. A detailed analysis of the deformation modes shows that the numerous dislocations slippages and deformation twinning in the αp phase are the main reasons for the high ductility, and the acicular αs phase provides the alloy with high strength after heat treatment. This newly developed alloy is a potential material for various structural applications. [ABSTRACT FROM AUTHOR]

In this study, CoCrFe and CoCrFeNi transition high entropy alloys (HEAs) are modelled by extended tight-binding density functional theory (DFT) method. Also, the geometric optimizations, band structures, density of states (DOS), thermodynamic properties and phonon dispersion curves of alloys are investigated to give a detailed information. The results show that the covalent d-d bonding between Fe-Cr is occurred because of strong metallic Cr-Fe interactions. The entropy (S) value increases gradually with the addition of Ni element to the CoCrFe alloy. The heat capacity (Cv) increases due to the harmonic effect of the phonons in the range of 0-400 K and then, close to the classic limit at high temperatures with 0.82 J/mol.K and 0.94 J/mol.K for the CoCrFe and the CoCrFeNi. The alloy systems exhibit metallic properties because the DOS of the metals have a nonzero value at the Fermi energy level. Also, the addition of element Ni to the CoCrFe alloy system causes a decrease in phonon frequencies. [ABSTRACT FROM AUTHOR]

Spinodal phase separation in SMART (Self-passivating Metal Alloys with Reduced Thermo-oxidation) materials based on binary W-Cr with alloying elements Y and Zr is systematically investigated by a combination of Density Functional Theory with Cluster Expansion Hamiltonian and large-scale Monte Carlo simulations with thermodynamic integration. Comparing alloys of Zr with those of Y in ternary compositions with W and Cr, it is shown that there is a significant difference in the average short-range order between W and Zr, which changes from positive to negative from 500 K to higher temperatures in W70Cr29Zr1 alloys compared with the positive SRO (Short-Range Order) between W and Y in W70Cr29Y1 alloys at all temperatures. This change, however, does not affect the segregation behavior between W and Cr in the whole range of temperature between these alloys. Importantly, it is found that co-segregation of Y and Zr due to the negative SRO between them, in W70Cr29Y0.5Zr0.5 and W70Cr28Y1Zr1 considered alloys, increases the W-Cr positive SRO closer to the binary W70Cr30. Our modeling results reveal a significant impact on spinodal phase segregation of W and Cr in designing SMART materials for DEMO devices of future fusion power plants. Findings from recent experimental studies validate the modeling results, particularly the high-temperature behavior of the W-Cr-Zr alloys and the microstructure evolution of the W-Cr-Y-Zr alloys. The results provide a fundamental understanding of the radiation resistance phenomena observed in recent experiments on neutron-irradiated self-passivating alloys.

Nickel-copper chromite (NiCuCr2O4) was synthesized by the co-precipitation method using sodium hydroxide as a precipitating agent. The composition of ammonium nitrate (AN):NiCuCr2O4 (mass ratio 98:2) was used for the comparative thermal analysis study. The results suggested that ammonium nitrate containing nickel-copper chromite (AN + NiCuCr2O4) can act as a potential energetic material to replace AN in energetic applications. The activation energy of AN + NiCuCr2O4 was decreased by 85.7 kJ mol−1 compared to pure AN along with a reduction in the peak decomposition temperature. The lower activation energy and low pre-exponential factor can fasten AN + NiCuCr2O4’s decomposition at a lower temperature.

This study investigates the impact of a high-entropy alloy filler metal coated with copper (Cu) and post-weld heat treatment (PWHT) on the weldability of a ferrous medium-entropy alloy (MEA) in gas tungsten arc welding. The addition of 1-at% Cu had an insignificant effect on the microstructural behaviour, despite a positive mixing enthalpy with other elements. It was observed that a small amount of Cu was insufficient to induce phase separation into the Cu-rich phase and refine the microstructure of the as-welded specimen. However, with an increase in the PWHT temperature, the tensile strength remained mostly consistent, while the elongation significantly increased (elongation of as welded, PWHT700, PWHT800, and PWHT 900 were 19, 43, 55 and 68%, respectively). Notably, the PWHT temperature of 900 °C yielded the most desirable results by shifting the fracture location from the coarse-grained heat-affected zone (CGHAZ) to base metal (BM). This was due to significant recrystallisation and homogenised hardness of the cold-rolled BM during PWHT. However, the CGHAZ with coarse grains induced by the welding heat input remained invariant during the PWHT. This study proposes a viable PHWT temperature (900 °C) for enhancing the weldability of cold-rolled ferrous MEA without additional process.

In this work, derivation of the main thermodynamic relationships is realized together with the applied calculation of some parameters, providing the systematized description of non-linear thermo-mechanical deformation at dynamic mechanical analysis (DMA). Obtained equations and values agree well with experiments on different ribbon metallic glasses. We generalize the main initial conditions (i.e., experimental and numerical parameters) by that the proposed model can be used for the investigation of DMA in different materials. The further opportunities of the found approach are also discussed in frames of phase transitions in metallic glass. [ABSTRACT FROM AUTHOR]