Structure Of Alloys Research Articles

Structure and properties of Fe40Mn20Cr20Ti10Al10 high-entropy alloy fabricated by mechanical alloying and spark plasma sintering

Structure and properties of Fe40Mn20Cr20Ti10Al10 high-entropy alloy fabricated by mechanical alloying and spark plasma sintering

Effect of Annealing Time on Grain Structure Evolution and Superplastic Response of Al-Mg 5xxx Alloys

The impact of annealing on the recrystallized grain structure and superplastic behavior of two Al-Mg 5xxx alloys used for high-speed blow forming (HSBF) was studied. The results revealed that both alloys demonstrated rapid static recrystallization after only a few minutes of annealing at 520 °C, forming fine and equiaxed grain structures. After four min of annealing, Alloy 2 (Al-4.0Mg-1.18Mn) exhibited a higher fraction of small grains (<10 µm) compared to Alloy 1 (Al-4.5Mg-0.74Mn). Moreover, Alloy 2 displayed enhanced resistance to grain coarsening with increasing annealing times, which was attributed to its higher amount of Al6(Mn,Fe) intermetallic particles and a higher number density of Mn dispersoids. Optimizing the annealing time can effectively develop a fine and stable grain structure in Al-Mg 5xxx alloys. During tensile deformation, Alloy 2 consistently showed higher ductility compared to Alloy 1 at low strain rates (170% vs. 138% at 0.001 s−1 and 163% vs. 134% at 0.01 s−1), whereas at a high strain rate of 1 s−1, both alloys displayed comparable tensile elongation. The high superplastic response of Alloy 2 at low strain rates renders it a superior superplastic alloy for HSBF applications.

Asynchronous Spheroidization of the Lamellar Structure in a Near-α Ti Alloy

Asynchronous Spheroidization of the Lamellar Structure in a Near-α Ti Alloy

Radiation Resistivity of Ti-5331 Alloy with Different Microstructures

Titanium alloys have promising potential for applications in marine nuclear power systems owing to their exceptional mechanical and corrosion properties. Nevertheless, their radiation resistivity is a determining factor for their extensive use as structural materials in nuclear energy systems. In this study, the radiation resistivity of Ti-5Al-3V-3Zr-Cr (Ti-5331) alloys with three different microstructures was examined using a combination of characterization techniques including positron annihilation Doppler broadening spectroscopy (DBS), Elastic Recoil Detection Analysis (ERDA), Transmission Electron Microscope (TEM), Small-Angle X-ray scattering (SAXS) and nanoindentation. The results reveal that the equiaxed structure, bimodal structure, and Widmanstatten structure of Ti-5331 alloy obtained through different annealing processes exhibit differences in the number of interfaces and the content of the β phase. The α/β interfaces can significantly enhance the radiation resistance of titanium alloys by inhibiting the diffusion of helium atoms after helium ion irradiation. Notably, the alloy with a bimodal structure exhibited the best overall radiation resistivity, showing small defect size, low hardening effect, and low swelling rate of 0.003%. Moreover, the size of helium bubbles of the bimodal structure is half of that in the equiaxed structure and Widmanstatten structure. Thus, the bimodal structure of the Ti-5331 alloy possesses superior radiation resistivity.

Effect of Al/Cr ratio on structure, magnetism, and corrosion resistance of FeCoNiCr1-xAlx high entropy alloys

This study investigates the microstructure, magnetic properties, and corrosion resistance of FeCoNiCr1-xAlx (x=0, 0.25, 0.5, 0.75, 1) high-entropy alloys using the combination of experimental methods and first-principles calculations. XRD results reveal the FCC-BCC phase transition as x increases, and FeCoNiCr1-xAlx exhibits a noticeable dual-phase structure when x=0.75. The partial segregation between Ni and Al elements is indicated by SEM-EDS observations. The magnetism of both FCC and BCC phases become strong with increasing x, and the BCC phase consistently exhibiting higher magnetism than the FCC phase. Potentiodynamic polarization curves show that Al0.25 has the highest corrosion potential and the lowest corrosion current density. Under open circuit potential conditions, due to the difference between the corrosion potential and the open circuit potential, the electrochemical impedance spectroscopy measurements indicate that the corrosion resistance of the alloys follows the order: Al0 > Al0.5 > Al0.75 > Al0.25 > Al1. Considering both the soft magnetic behavior and corrosion resistance, Al0.75 is a optimal choice. These findings provide valuable insights for developing magnetic high-entropy alloy materials with superior corrosion resistance.

Evading the strength-ductility trade-off dilemma in high-entropy alloy by lamellar structure

Constructing lamellar structures in high-entropy alloys (HEAs) is an effective strategy for addressing the inherent trade-off between strength and ductility. However, conventional processing methods often struggle to achieve precise control over the microstructures and mechanical properties of the lamellar structures. Here, we employ laser remelting technology to successfully fabricate a lamellar structure within an HEA. The lamellar HEA shows an excellent yield strength of ∼547 MPa with a large uniform elongation of ∼41 %. Such enhanced strength-plasticity synergy is mainly attributed to the hetero-deformation of lamellar structures.

Structure of the metal matrix Mo-based alloy produced by the EBM method

Structure of the metal matrix Mo-based alloy produced by the EBM method

Research on the Effect of Quasi-β Forging Deformation on the Structure and Properties of TC21 Titanium Alloy

Research on the Effect of Quasi-β Forging Deformation on the Structure and Properties of TC21 Titanium Alloy

Effect of trace Bi addition on the microstructure and mechanical properties of hypoeutectic Al-Mg-Si-Mn alloy

The effects of Bi on the eutectic structure and mechanical properties of AlMg5Si2Mn alloy were investigated. The results show that when trace Bi is added to the alloy, the eutectic Mg2Si phase in the alloy is successfully refined from long plate-like to fine fiber rod-like and coral-like structure. It is mainly attributed to the precipitation of Bi atomic clusters on the front of the solid-liquid interface and form a component supercooling, in which part of Bi atoms react with Mg atoms to form nanosized Mg3Bi2 particles, which effectively inhibits the rapid growth of eutectic Mg2Si and promotes the branching and refining of eutectic Mg2Si. The strength and ductility of AlMg5Si2Mn alloy containing Bi are significantly improved simultaneously. Compared to the unmodified alloy, the largest tensile strength, yield strength and elongation to failure of the 0.3wt % Bi-modified alloy are increased to 28.04%, 12.3% and 129.1%, respectively. The fracture mode of the alloy changes from brittle fracture to ductile fracture.

A comparative investigation of the thermal stability and oxidation resistance of AlCrSiWN and AlCrSiN/AlCrWN coatings

Alloying and multi-layer structure design are two important methods for modifying AlCrN-based coatings. In this study, AlCrSiWN alloyed and AlCrSiN/AlCrWN multi-layer coatings were deposited using cathodic arc evaporation (CAE) technique to investigate their differences in thermal stability and resistance to high-temperature oxidation. The results indicate that, (1) Both coatings exhibit a c-Al(Cr) N single-phase structure, while the AlCrSiN/AlCrWN coating possesses a finer grain structure as well as lower surface roughness. Therefore, AlCrSiN/AlCrWN coating exhibits a higher nanohardness (32.1 ± 2.8 GPa) at room temperature. (2) The thermal decomposition temperature of the AlCrSiWN coating (∼1045 °C) is slightly higher than that of the AlCrSiN/AlCrWN coating (∼1035 °C), and thus the nanohardness (31.3 ± 2.0 GPa) of the AlCrSiWN coating after annealing at 1000 °C is higher than that of the AlCrSiN/AlCrWN coating (28.1 ± 1.0 GPa). (3) The different modification strategies mad both coatings have comparable oxidation resistance at temperature below 1200 °C. However, at a higher temperature (>1200 °C), the AlCrSiWN coating demonstrated superior resistance to high temperature oxidation compared to the AlCrSiN/AlCrWN coating.

A very simple synthesis of defect-rich PdAg nanosponges for highly selective hydrogenation of furfural

Furfuryl alcohol (FA) is an important chemical and has extensive applications in varied fields. To realize the highly selective hydrogenation of furfural (FF) to produce FA, the key is the preparation of the catalysts with excellent performance. Herein, a very simple wet chemical method is developed for the one-step preparation of PdAg nanosponges (NSs). Specifically, with Pd(OAc)2 and AgNO3 as precursors, and ethylene glycol (EG) as both solvent and reducing agent, PdAg NSs can be grown and assembled at mild temperature of 40 °C. Throughout the reaction, no any surfactants and additional reducing agents are applied. The as-prepared PdAg NSs possess 3D self-supported alloy structures, “clean” surface, abundant pores, high specific surface area and rich defects. In the FF hydrogenation reaction at 60 °C under 1.5 MPa H2 pressure in the mixed solvent of ethanol and water (1 : 4 in volume ratio), the self-supported PdAg-1 NSs (1 : 1 in Pd/Ag molar ratio) exhibit superior catalytic performance than other PdAg NSs, pure Pd sample and commercial Pd/C (10%). With PdAg-1 NSs as catalyst in the absence of support, 100% FF can be converted and the selectivity toward FA is as high as 97.1% at 36.0 h of reaction. After 4 cycles, PdAg-1 NSs still maintain the high catalytic activity in FF hydrogenation and high selectivity toward FA, which may originate from the 3D self-supported structures, high specific surface area, “clean” surface, rich defects and electronic synergistic effect between Pd and Ag. This simple fabrication of PdAg NSs introduces new ideas for the synthesis of other nanostructured bi- and multi-metallic catalysts for highly selective FF hydrogenation to FA and other advanced applications.

Estimation of hydrides structure and mechanical properties of irradiated E110 alloy after thermomechanical tests imitating dry storage conditions

Safety assurance of spent nuclear fuel dry storage requires reliable prediction of mechanical properties of fuel element cladding depending on structural changes at all stages of nuclear fuel handling. In this work investigations of hydrides structure in irradiated fuel element cladding made of E110 alloy have been conducted in irradiated state as well as after tests simulating dry storage conditions. Using the program code, the coefficients that best correlate with mechanical properties have been found.

IMPROVEMENT OF THE ALLOY STRUCTURE OF THE Ni-Cr-Со-W-Mo-Al-Ti-C SYSTEM

Purpose. Establishing the specifics of the influence of alloying elements on the formation of carbides in the structure, their shape and the possibility of separating TLC phases for the system of the Ni-Cr-Co-W-Mo-Al-Ti-C type using the CALPHAD calculation method of prediction in comparison with data obtained by the method of raster electron microscopy. Research methods. The results of experimental and calculated data, formed on the basis of experimental and results taken from open sources, are presented. The chemical composition was determined on a REM-106I scanning electron microscope equipped with an energy dispersive analysis. Experimental values were processed by the method of least squares with obtaining correlation dependencies of the “parameter-property” type and establishing mathematical equations of regression models that optimally describe these dependencies. Results. It was established that when the concentration of titanium is more than 4 % and molybdenum is more than 6 % and 15 % chromium, the formation of TSC phases (Р, s and m- phases) is possible, which reduce the operational properties of the alloy. It was found that when the alloy contains more than 25 % chromium, a solid chromium-based solution is formed, which reduces the properties of the alloy (mechanical and corrosion). It is shown that the obtained dependences correspond to reality and coincide with experimental data at the level of 10 %. Scientific novelty. Obtained dependences of the influence of alloying elements on the chemical composition of carbides will allow predicting properties without conducting experiments. It was established that changes in the course of dependencies are closely correlated with the processes occurring in the structure of alloys. Practical value. The obtained dependencies can be used both for the development of new heat-resistant alloys and for the improvement of the compositions of industrial alloys.

Dynamic Behavior of Pt Multimetallic Alloys for Active and Stable Propane Dehydrogenation Catalysts.

Improving the use of platinum in propane dehydrogenation catalysts is a crucial aspect to increasing the efficiency and sustainability of propylene production. A known and practiced strategy involves incorporating more abundant metals in supported platinum catalysts, increasing its activity and stability while decreasing the overall loading. Here, using colloidal techniques to control the size and composition of the active phase, we show that Pt/Cu alloy nanoparticles supported on alumina (Pt/Cu/Al2O3) displayed elevated rates for propane dehydrogenation at low temperature compared to a monometallic Pt/Al2O3 catalyst. We demonstrate that the enhanced catalytic activity is correlated with a higher surface Cu content and formation of a Pt-rich core and Cu-rich shell that isolates Pt sites and increases their intrinsic activity. However, rates declined on stream because of dynamic metal diffusion processes that led to a more uniform alloy structure. This transformation was only partially inhibited by adding excess hydrogen to the feed stream. Instead, cobalt was introduced to provide trimetallic Pt/Cu/Co catalysts with stabilized surface structure and stable activity and higher rates than the original Pt/Cu system. The structure-activity relationship insights in this work offer improved knowledge of propane dehydrogenation catalyst development featuring reduced Pt loadings and notable thermal stability for propylene production.

Origin of unique electronic structures of single-atom alloys unraveled by interpretable deep learning.

We uncover the origin of unique electronic structures of single-atom alloys (SAAs) by interpretable deep learning. The approach integrates tight-binding moment theory with graph neural networks to accurately describe the local electronic structure of transition and noble metal sites upon perturbation. We emphasize the complex interplay of interatomic orbital coupling and on-site orbital resonance, which shapes the d-band characteristics of an active site, shedding light on the origin of free-atom-like d-states that are often observed in SAAs involving d10 metal hosts. This theory-infused neural network approach significantly enhances our understanding of the electronic properties of single-site catalytic materials beyond traditional theories.

Post-Fire Stability Bearing Capacity of I-Shaped Aluminum Alloy Members Under Axial Compression

Compared to steel structures, aluminum alloy structures are more susceptible to fire damage. Accurately evaluating the residual bearing capacity of fire-damaged aluminum alloy members is crucial for effective post-disaster management. Therefore, this paper investigates the post-fire bearing capacity of I-shaped aluminum alloy members under axial compression. First, a post-fire test on 16 I-shaped aluminum alloy members under axial compression was carried out. The test results indicate that all specimens fail by the minor axis flexural buckling, and the bearing capacity of the specimens decreases with the increase of the slenderness ratio. Moreover, a trilinear relationship is found between bearing capacity and post-fire temperatures. Second, finite element (FE) models are established using ABAQUS and validated against the test results. Subsequently, numerical analysis is carried out, considering various aluminum alloy brands, post-fire temperatures, slenderness ratios, initial geometrical imperfections, and cross-section dimensions. Through the statistical regression technology and the introduction of strength and stability-bearing capacity reduction coefficients, the formulae for estimating the post-fire stability-bearing capacity of I-shaped aluminum alloy members under axial compression are derived. Finally, the proposed formulae are verified to be accurate through error analysis.

Evolution from micropinned to polymeric alloy structure of XLPE‐PS: Improving electrical properties and mechanism

AbstractThis research investigates the transition from a micropinned to a polymeric alloy structure in crosslinked‐polyethylene‐polystyrene (XLPE‐PS). Incorporating 2 wt% 10 μm PS particles into low‐density polyethylene (LDPE) and crosslinking with 2 wt% dicumyl peroxide (DCP) forms XLPE‐PS structures. The polymeric alloy structure, formed at 220°C extrusion, contrasts with the micropinned formed at 150°C. Morphological, thermo‐structural, chemical, and crystal properties are examined to understand their impact on electrical properties and charge transport mechanisms. Results indicate that the polymeric alloy effectively resolves void/crack issues, whereas the micropinned exhibits phase separation. Both structures exhibit a benzene‐crosslinked network, and variations in these structures lead to significant changes in thermo‐structural, chemical, and crystalline properties. The polymeric alloy XLPE‐PS shifts the polyethylene (PE) hkl crystal planes, confirming phase shift and optimal alloying. The structural alterations reveal deeper traps and higher densities in the polymeric alloy XLPE‐PS, leading to significantly improved electrical properties, including reduced DC conductivity by up to 1.3 and 0.7 decades at 30 and 90°C, and increased DC breakdown strength by up to 40.34% and 16.17% at 30 and 90°C, respectively, compared with micropinned XLPE‐PS. This research offers insights into stable high‐voltage insulation development.

Comparative Study of Life-Cycle Environmental and Cost Performance of Aluminium Alloy–Concrete Composite Columns

As is widely known, the construction industry is one of the sectors with a large contribution to global carbon emissions. Despite numerous efforts in the construction industry to develop low-carbon materials, there is a limited number of studies quantifying and presenting the overall environmental impact when these materials are applied in a construction project as structural members. To address this gap, this study focuses on assessing the life-cycle performance of novel structural aluminium alloy–concrete composite columns. In this paper, the environmental impacts and economic aspects of a concrete-filled aluminium alloy tubular (CFAT) column and a concrete-filled double-skin aluminium alloy tubular (CFDSAT) column were assessed using life-cycle assessment (LCA) and life-cycle cost analysis (LCCA) approaches, respectively. The cradle-to-grave system boundary is considered for these analyses to cover the entire life-cycle. A concrete-filled steel tubular (CFST) column is also assessed for reference. All columns are designed to have the same load-carrying capacity and, thus, are compared on a level-playing basis. A comparison is also made of the self-weight of these columns. In particular, the self-weight of the CFST column is reduced by around 17% when the steel tube is replaced by an aluminium alloy tube, and decreased by 47% when the double-skin technique is adopted in CFDSAT columns. The LCA results indicate that the CO2 emission of CFST and CFAT is almost the same, which is 21% less than the CFDSAT columns due to the use of high aluminium in the latter. The LCCA results show that the total life-cycle cost of CFAT and CFDSAT columns is around 29% and 14% lower, respectively, than that of the CFST column. Finally, a sensitivity analysis was carried out to evaluate the effects of data and assumptions on the life-cycle performance of the examined columns.

CO2-assisted Controllable Synthesis of PdNi Nanoalloys for Highly Selective Hydrogenation of Biomass-derived 5-Hydroxymethylfurfural.

The selective hydrogenation of 5-hydroxymethylfurfural (HMF) to 2,5-bishydroxymethyltetrahydrofuran (BHMTHF), a vital fuel precursor and solvent, is crucial for biomass refining. Herein, we report highly selective and stable PdNi nanoalloy catalysts for this deep hydrogenation process. A CO2-assisted green method was developed for the controllable synthesis of various bimetallic and monometallic catalysts. The PdNi/SBA-15 catalysts with various Pd/Ni ratios exhibited a volcano-like trend between BHMTHF yield and Pd/Ni ratio. Among all catalysts tested, Pd2Ni1/SBA-15 achieved the best performance, converting 99.0% of HMF to BHMTHF with 96.0% selectivity, surpassing previously reported catalysts. Additionally, the Pd2Ni1/SBA-15 catalyst maintained excellent stability even after five recycling runs. Catalyst characterizations (e.g., HAADF-STEM) and DFT calculations confirmed the successful formation of the alloy structure with electron transfer between Ni and Pd, which accounts for the remarkable performance and stability of the catalyst. This work paves the way for developing highly selective and stable alloy catalysts for biomass valorization.

The Effect of Cooling Rate on Solidification Characteristics and Grain Structure of Al-9Si Cast Alloy

A thermal analysis study is essential before the semisolid metal processing of a particular alloy. The surrounding environment, especially the cooling rate is also an important factor. This study investigated the influence of different cooling rates on the solidification characteristics and microstructure evolution of the Al-9Si cast alloy. Four cooling mediums were designed, and their cooling rates are 0.16 ℃/s, 1.0 ℃/s, 1.3 ℃/s, and 1.9 ℃/s, respectively. The results show that the primary dendrite size of the Al-9Si alloy was reduced from 162.61 μm to 86.86 μm as the cooling rate increased from 0.16 ℃/s to 1.9 ℃/s. Significant grain refinement was observed, however, the external cooling has a negligible impact on solid fraction. The optimal temperature range of the Al-9Si cast alloy for the semisolid metal processing at a solid fraction of 0.5 to 0.7 is between 554 ℃ and 563 ℃. With these thermal profiles provided, the relationship between the solid fraction and the solidification time could be expressed using the polynomial equation, which is also useful for point prediction in the subsequent semisolid metal processing.