Alloy Interface Research Articles

Preparation and property modulation of three-dimensional bicontinuous graphite/aluminum alloy composites

In this paper, porous graphite skeletons were rapidly prepared using selective laser sintering (SLS) molding technique. After several vacuum impregnation reinforcements, carbonization, graphitization and surface modification, the porous graphite skeleton has good compressive strength and thermal-physical properties. A356 aluminum alloy was compounded with porous graphite skeleton by vacuum extrusion casting method to obtain three-dimensional bicontinuous graphite/aluminum alloy composites. The effects of vacuum impregnation reinforcement on the comprehensive properties of the porous graphite skeleton were investigated, and the bending strength, thermal conductivity (TC) and coefficient of thermal expansion (CTE) of the three-dimensional bicontinuous graphite/aluminum alloy composites were regulated by changing the volume fraction of the porous graphite skeleton. In the composites, the porous graphite skeleton bonded well with the aluminum alloy interface. The various properties of the composites showed significant anisotropy of each by the influence of the porous graphite skeleton. When the volume fraction of porous graphite skeleton is 55 %, the bending strength of three-dimensional bicontinuous graphite/aluminum alloy composite reaches 75.8 MPa, TC reaches 116.84 W/m K, and CTE reaches 6.11 × 10-6 K−1, which is expected to be a potential thermal management material.

Improving the high temperature oxidation resistance of TiAl alloy by SiOC coating

To improve the high temperature oxidation resistance of TiAl alloy, silicon oxycarbide (SiOC) coating was fabricated by dip-coating using polydimethylsiloxane (PDMS) as the precursor. The oxidation behavior of the coating was evaluated at 850 °C. The morphology and chemical structure of the SiOC coating were characterized by scanning electron microscopy (SEM) equipped with an energy dispersive spectroscopy (EDS), Fourier Transform infrared spectroscopy (FT-IR), X-ray photo electron spectroscopy (XPS), and X-ray diffraction (XRD). Results showed that the SiOC coating exhibited good oxidation resistance. During the thermal exposure, the selective oxidation of Al at the SiOC/TiAl alloy interface resulted in the generation of protective Al2O3, which suppressed the inward diffusion of oxygen and outward diffusion of the alloy matrix elements. However, the cracks on the surface of SiOC coating were observed, which would provide channels for the oxygen and form thermally grown oxide layer (mainly consisting of TiO2 and Al2O3) above the Al2O3 layer.

Triple heat treatment effects of Inconel X-750 superalloy on its microstructure, hardness, and high-temperature fretting wear characteristics

Inconel X-750 alloy specimens were undergone the triple heat treatment process: solution annealing (1149 °C/2h), equalization treatment (843 °C/24h), and precipitation treatment (704 °C/20h). Then microstructure characterization and hardness tests were performed prior to the self-mated pin-on-disk fretting wear tests in the range of 25 °C-650 °C temperature conditions. This type of alloys is widely used in bump-type gas foil bearing applications where complex fretting phenomenon occurs between foils under harsh operating conditions. Conducted investigations revealed that the heat-treated sample developed more precipitated phases in the matrix and along the grain boundaries with higher bulk hardness. Fretting wear surface morphologies indicate that the formation of glaze layer composed of NiO, Cr2O3, and mixed Ni(Fe,Cr)2O4 oxides prevail on the wear scar during the elevated temperatures, harnessing significantly lower friction coefficient and wear loss. Severe material transfers and galling were the dominant wear mechanism in the non-heat-treated alloy interface which caused the stick-slip frictional behavior. On the contrary, the heat-treated alloy surfaces demonstrated the stable coefficient of friction and 3–10 times lower wear rates at high temperatures due to the additional Cr-rich carbides. It is believed that these hard and lubricious Cr2O3 internal oxide precipitates form healing glaze barrier in the interface by protecting against severe material transfer/build-up.

From Inside Out: How the Buried Interface, Shell Defects, and Surface Chemistry Conspire to Determine Optical Performance in Nonblinking Giant Quantum Dots

“Giant” or core/thick‐shell quantum dots (gQDs) are an important class of solid‐state quantum emitter characterized by strongly suppressed blinking and photobleaching under ambient conditions, and reduced nonradiative Auger processes. Together, these qualities provide distinguishing and useful functionality as single‐ and ensemble‐photon sources. For many applications, operation at elevated temperatures and under intense photon flux is desired, but performance is strongly dependent on the synthetic method employed for thick‐shell growth. Here, a comprehensive analysis of gQD structural properties “from the inside out” as a function of shell‐growth method is reported: successive ionic layer adsorption and reaction (SILAR) and high‐temperature continuous injection (HT‐CI), or sequential combinations of the two. Key correlations across synthesis methods, structural features (interfacial alloying, stacking‐fault density and surface‐ligand identity), and performance metrics (quantum yield, single‐gQD photoluminescence under thermal/photo stress, charging behavior and quantum‐optical properties) are identified. Surprisingly, it is found that interfacial alloying is the strongest indicator of gQD stability under stress, but this parameter is not the determining factor for Auger suppression. Furthermore, quantum yield is strongly influenced by surface chemistry and can approach unity even in the case of high shell‐defect density, while introduction of zinc‐blende stacking faults increases the likelihood that a gQD exhibits charged‐state emission.

Electrochemical behaviour of the Al-20Mg alloy in synthetic seawater with alkaline pH

The corrosion of Al-(20 wt%) Mg alloy in artificial seawater solution at different pH, using potentiodynamic polarization, polarization resistance and electrochemical impedance spectroscopy techniques was assessed. The results showed that the effect of the pH of the artificial seawater solution promoted susceptibility to localized corrosion by dissolution of the oxide layer, which is naturally present on the surface of the aluminium alloy. X-ray diffraction analysis shows the presence of Al3Mg2 intermetallic phase which promotes the dissolution of the aluminium phase, and the evolution of hydrogen. The activation mechanism at the oxide-free zones and the diffusion through the corrosion products scale were associated with continuous formation of Al(OH)3 and Mg(OH)2 at the Al-Mg alloy interface, with minor protective effect as pH increases. The electrochemical behaviour of the Al-(20 wt%)Mg alloy in artificial seawater solution at pH 14 suggests potential application in hydrogen evolution due to its high surface catalytic activity. Results were complemented by scanning electron microscopy and X-ray diffraction characterization.

Vacuum brazing of SiCp/Al composites and TC4 titanium alloy: Microstructure evolution and mechanical properties

In this paper, a dissimilar material consisting of 55% SiCp/ZL102 composites and TC4 titanium alloy was brazed using Al-8.0 Mg-17.0Cu-1.0Ti foil-like brazing alloy manufactured by rapid solidification technology. Brazing was completed in a vacuum of 1.0 × 10−4 Pa. Si element from Al composites accumulated at the interface of TC4 titanium alloy to form Ti7Al5Si12 intermetallic compound layer. The intermetallic compound α2(TiAl3) grew perpendicular to the brazing seam below 590 °C. The α2(TiAl3) intermetallic compound grown into long strips at 590 °C. The strip structure had a bonding interface in the form of pinning at a certain angle. The brazing interface was continuous and dense, without defects and exhibited good bonding performance. The shear strength of the brazed joint reached 98.01 MPa at 590 °C for 30 min, and the gas tightness was 1.0 × 10−10 Pa m3/s. The brazed joint failed in filler metal due to ductile-brittle mixed fracture mechanism, which resulted in shear lips, parabolic dimples, and furrows in the fracture surface.

Synergistically Stabilizing Thin Li Metal through the Formation of a Stable and Highly Conductive Solid Electrolyte Interface and Silver-Lithium Alloy.

In this study, a stable solid electrolyte interface (SEI) and a Ag-Li alloy were formed through a simple slurry coating of silver (Ag) nanoparticles and Li nitrate (LiNO3) on a Li metal surface (AgLN-coated Li). The Ag-Li alloy has a high Li diffusion coefficient, which allowed the inward transfer of Li atoms, thus allowing Li to be deposited below the alloy. Moreover, the highly conductive SEI enabled the fast diffusion of Li ions corresponding to the alloy. This inward transfer resulted in dendrite suppression and improved the Coulombic efficiency (CE). The AgLN-coated Li exhibited an initial capacity retention >81% and CE > 99.7 ± 0.2% over 500 cycles at a discharge capacity of 2.3 mA h cm-2.

Energy and morphology of martensite–twinned martensite interface in CuAlNi shape memory alloy: A phase-field study

Needle-like twins are observed experimentally within the transition layer at the martensite–twinned martensite interface. We utilize a phase-field approach to investigate this microstructure. Our goal is to simulate the morphology of the transition layer and to perform a detailed analysis to characterize its interfacial and elastic micro-strain energy. To illustrate the micromechanical framework developed for that purpose, sample computations are carried out for a CuAlNi shape memory alloy undergoing a cubic-to-orthorhombic martensitic transformation. A particular focus of the study is on size-dependent morphology through examining the impact of twin spacing. Additionally, our results reveal that certain twin volume fractions lead to the emergence of twin branching as a way to minimize the total free energy stored in the microstructure.

High Capacity Sn Metal Anode for Aqueous Proton-Based Batteries

Aqueous proton-based batteries (APBs) as a good choice to respond battery diversity, delivering safety, cost, environmental friendliness and high-power necessary for renewable energy storage.1 However, most promising conventional aqueous battery anodes have relatively poor compatibility in acid. The limited existing anode options like Pb and MoO3 can hardly match the high-performance of advanced cathodes, leading low-voltage and unsatisfactory energy density of APBs.2-4 Therefore, the exploration of high-performance anode materials is thus of critical issue for the APB assembling.Sn metal should be one of the most suitable APB anode choices due to its relatively high hydrogen evolution reaction (HER) overpotential, large theoretical capacity (451.6 mAh g−1) and negative redox potential (−0.14 V vs. SHE). With a body-centered tetragonal crystal structure and similar facet surface energy, Sn metal deposit in polyhedral morphology isotropically. This may cause serious “dead Sn” issue when deposition capacity increases because large Sn particle has limited contact with the substrate and easily to shed from the electrode, resulting in low Coulombic efficiency and short lifespan.We will present our efforts of developing Sn anode with high capacity and long lifespan by an interfacial alloying regulation approach. Smaller grain size and more uniform Sn deposition can be achieved by higher propensity for nucleation and Sn migration energy barrier. Extra interfacial interaction suppresses shedding of Sn polyhedron particles, thus prohibiting the formation of “dead” Sn. Based on the optimized Sn metal anode, we propose several promising designs for APBs, with high performance such as high output voltages, good specific energy densities, fast kinetics, and long life. References X. Wu, J. J. Hong, W. Shin, L. Ma, T. Liu, X. Bi, Y. Yuan, Y. Qi, T. W. Surta, W. Huang, J. Neuefeind, T. Wu, P. A. Greaney, J. Lu, X. Ji. Nat. Energy 2019, 4, 123-130.W. Chen, G. Li, A. Pei, Y. Li, L. Liao, H. Wang, J. Wan, Z. Liang, G. Chen, H. Zhang, J. Wang, Y. Cui. Nat. Energy 2018, 3, 428-435.Y. Liang, Y. Jing, S. Gheytani, K. Y. Lee, P. Liu, A. Facchetti, Y. Yao. Nat. Mater. 2017, 16, 841-848.X. Wang, Y. Xie, K. Tang, C. Wang, C. Yan. Angew. Chem. Int. Ed. 2018, 57, 11569-11573.

Preparation Method and Properties of Q235/5083 Composite Plate with 1060 Interlayer by Differential Temperature Rolling with Induction Heating

Due to their exceptional all-around performance, steel/aluminum-alloy composite plates have been frequently utilized in many different industries. However, when steel/aluminum-alloy composite plates are prepared by the rolling process, they will scarcely bond with high bonding strength under a lower reduction rate due to the inconsistent deformation the of steel/aluminum-alloy. Therefore, a method of adding a pure-aluminum interlayer by differential temperature rolling with induction heating was proposed to prepare steel/aluminum-alloy composite plates. The results showed that when the induction heating time was 10–18 s, the pure-aluminum interlayer became molten, and the temperature difference between the steel and aluminum alloy reached 350–500 °C. The interface shear strength of the composite plate reached more than 68 MPa under a 31% reduction rate. The shear fracture of the composite plate occurred in the pure-aluminum layer, and the steel/aluminum interface diffusion layer was 0.83–0.99 μm thick. There was no obvious compound formation at the bonding interface, however, the steel and aluminum alloy could not bond without the addition of an interlayer under the same conditions.

Structure and diffuseness model of solid-liquid interface for binary alloys

Using the morphological instability at the solid–liquid interface as a basis by the maximum entropy production rate principle (MEPR), a model is presented on the morphological structure and diffuseness of the interface during directional solidification of binary alloys. It is shown that, the independent diffuseness theory of Cahn and the Jackson roughness criterion can be unified at a limiting condition under this new MEPR solidification model. The model under the principle of MEPR is applied to describe the evolution of atomistically smooth and rough interfaces through the evaluation of the size of the solid–liquid interface and the of number atomic layers. The model is tested with data for binary alloys of aluminium, lead, and tin at varying solute concentrations. The results showed strong agreement with available data from experimental measurements.

Investigating electrochemical corrosion at Mg alloy-steel joint interface using scanning electrochemical cell impedance microscopy (SECCIM)

Developing strategies to prevent corrosion at the interface of dissimilar metal alloys is challenging because of the presence of heterogenous distribution of galvanic couples and microstructural features that significantly change the corrosion rate. Devising strategies to mitigate this interfacial corrosion requires quantitative and correlative understanding of its surface electrochemical reaction. In this work, scanning electrochemical cell impedance microscopy (SECCIM) was employed to study location-specific corrosion in the interfacial region of dissimilar alloys, such as AZ31 (magnesium alloy) and DP590 (steel) welded using the Friction-stir Assisted Scribe Technique (FAST) processes. Herein, SECCM and SECCIM were used to perform correlative mapping of the local electrochemical impedance spectroscopic and potentiodynamic polarization to measure the effect of electronic and microstructural changes in the welded interfacial region on corrosion kinetics. Microstructural characterization including scanning electron microscopy and electron backscatter diffraction was performed to correlate changes in microstructural features and chemistry with the corresponding electronic properties that affect corrosion behavior. The variations in corrosion potential, corrosion current density, and electrochemical impedance spectroscopy behavior across the interface provide deeper insights on the interfacial region—which is chemically and microstructurally distinct from both bare AZ31 and DP590 that can help prevent corrosion in dissimilar metal structures.

Tribological Performance and Model Establishment of Self-Compensating Lubrication Film Inspired by the Functional Surfaces of Scapharca subcrenata Shells

Composite surface structures inspired by the functional surface of Scapharca subcrenata shells can improve the tribological properties effectively, composed of the ordered “U”- shape micro-grooves and solid lubricant Sn-3.0Ag-0.5Cu (SAC305) alloys. A series of wear tests were conducted to further investigate the formation characteristics of the self-compensating lubrication film, and then the mathematical model of the spreading tribofilm could be proposed. The results showed that the appropriate surface texturing parameters (NBCSS-28) had a great effect on the formation of the self-compensating lubrication film, which exhibited a lower friction coefficient (0.386) and wear volume (0.682 mm3) than the other NBCSS samples. The tribofilm, with a thickness of a few microns, was deposited on the contact surface after the wear tests. The interfacial reactants (the Ni/Ni3Sn2 interface) of the SAC305 alloys, and Ni3Al alloys confirmed by the wetting experiments and the thermogravimetric analysis, could promote the deposition and diffusion of the tribofilm during the sliding process. Hence, distinguishable layered structures could be observed on the fractured surfaces of the NBCSS samples. Moreover, the formation process of the tribofilm exhibited an obvious relationship with the reduction in the dynamic friction coefficient. The tribofilm formation model was proposed by the accumulation behaviors of the spreading tribofilm randomly in the form of multiple discrete irregular film shapes on the worn surface, which could predict the formation characteristics of the self-compensating lubrication film to improve the optimization design of the parameters.

Dry reforming of methane for syngas production over noble metals modified M-Ni@S-1 catalysts (M = Pt, Pd, Ru, Au)

High tendency to sinter and carbon deposition becomes the choke point of Ni-based catalyst for its performance optimization in syngas generation via dry reforming of methane (DRM). Uniting the encapsulation of support with the construction of alloy interfaces, is a bright strategy to protect metallic Ni sites and synthesize highly efficient and stable Ni-based catalyst. Herein, M-Ni@S-1 catalysts (M = Pt, Pd, Ru, Au) with the same noble metal content (0.5 wt%) rather than moles were fabricated, and evaluated in DRM process. Results reveal that the type of noble metals influences the cooperating effect of the formed M − Ni alloy interface and support encapsulation degree, which achieves the best in Pt–Ni@S-1 catalyst. Therefore, Pt–Ni@S-1 catalyst exhibited outstanding sinter resistance and carbon tolerance as well as high catalytic stability, and obtained the highest methane conversion of approximately 80% at 700 °C and 60,000 mL·min−1·gcat−1 of GHSV. This can attribute to the small particle size of 3 nm, suitable metal-support interaction, abundant surface alkaline sites and stably existed Pt–Ni binary alloy interfaces.

Effect of Zn on Phase Evolution and Shear Resistance of Stainless Steel and Aluminum Alloy Interface by Laser Cladding

The connection between aluminum and iron alloys is of immense significance in the pursuit of lightweight industrial products. However, the Fe-Al interface’s inherent weakness restricts its widespread application. This study investigates the impact of Zn at the interface of Al-Fe laser cladding on the phase and mechanical properties of the interface. Specifically, we examine the influence of the applied Zn powder layer and alloying Zn layer on the morphology of the Fe-based cladding layer. The inclusion of Zn enhances the spreadability of the Fe-based cladding layer. Additionally, we elucidate the effect of Zn on the composition and phase of the Fe-Al laser cladding interface. Notably, the affinity between Zn and the η phase surpasses that of the θ phase, and an increased Zn content significantly thickens the η phase. Shear tests reveal that the failure mode of shear fracture encompasses both brittle and ductile fractures. Density functional theory (DFT) calculations indicate that Zn has a limited effect on the strength of the η phase but reduces the enthalpy of formation of the η phase. Our findings demonstrate that the alloyed Zn layer initially facilitates the formation of a continuous and uniform η layer, while an increased Zn content enhances and stabilizes the shear strength of the interface.

First-principles study of Re-W interactions and their effects on the mechanical properties of γ/γ′ interface in Ni-based single-crystal alloys

The distribution of solutes and their interactions play a crucial role in determining the mechanical properties of the γ/γ′ interface in Ni-based single-crystal alloys. In this study, atomic interactions between Re and W and their alloying effects on the inter-phase cohesion of the γ/γ′ interface are investigated by first-principles calculations. Our results show that W atom exhibits a preference for partitioning into the γ phase, while the stability of the γ/γ′ interface can be enhanced due to the partitioning of W to the γ′ phase. Moreover, our results reveal that partitioned W atoms in the γ′ phase contribute to the strengthening of the γ/γ′ interface. Conversely, the dissolution of W atoms in the γ phase weakens the inter-phase cohesion. However, this detrimental effect can be mitigated by introducing of Re into the γ/γ′ interface. Partitioning of Re and W into separate phases yields minimal alterations in interaction energies, resulting in a notable enhancement of inter-phase cohesion when compared to the partitioning of Re and W within γ phase of the γ/γ′ interface. Additionally, the partitioning of solute atoms at the γ/γ′ interface leads to local lattice distortion and interfacial energy reduction, which contribute to the enhancement of inter-phase cohesion of the γ/γ′ interface. As a result, a model is proposed for interpretation of crack propagation at the γ/γ′ interface at the threshold region with the presence of tensile stress in Ni-based single-crystal alloys.

Intrinsic Magnetic Proximity Effect at the Atomically Sharp Interface of CoxFe3-xO4/Pt Grown by Molecular Beam Epitaxy.

CoxFe3-xO4(CFO)/Pt bilayers prepared by molecular beam epitaxy were investigated for the anomalous Hall effect and X-ray magnetic circular dichroism (XMCD). We found that the anomalous Hall effect originates from a magnetic proximity effect at the CFO/Pt interface. The XMCD signal in the Pt L-edge was obtained only for the sample deposited at 600 °C, indicating that the magnetic proximity effect is sensitive to the interface structure. Transmission electron microscopy images of the CFO/Pt interface and XMCD measurements of Co and Fe L-edges do not provide direct evidence for interfacial atomic diffusion or alloying. In summary, these results suggest that the magnetic proximity effect is robust for transport properties, such as the anomalous Hall effect, while the induced magnetic moment depends on slight differences in the interfacial structure, such as the presence or absence of interfacial oxygen ions.

A new scheme for simulating diffusion-controlled growth in multi-component alloys

Simulation of diffusion-controlled phase growth has long been practiced by strictly following Fick-Onsager-Darken law for diffusion under the assumptions of local equilibrium and sharp interface. However, a major pain point is the difficulty of finding operating tie-lines at the interface for multi-component alloys. In the present work, a new scheme is presented to deal with this difficulty by extending from Larsson and Reed scheme (Larsson and Reed, Acta Mater. 56 (2008) 3754–3760). The flux balance equations are rewritten to enhance the accuracy and fulfilled from the very beginning of simulations. The simulation results of the Fe-Mn-Mo and Fe-C-Mn ternary systems, as well as high-order systems, demonstrate the applicability and robustness of the new scheme. The simulation of the Fe-C-Mn system reveals the details of the early stages of the bcc phase growth, showing a shrink of bcc before its growth with two growth modes smoothly switched.

Resistance element welding of aluminium alloy and steel using an element of aluminium

Aluminium alloy AA6061 and mild steel Q235 were welded by resistance element using an aluminium rivet as the element. The microstructure and properties of the joints were characterised. The temperature distribution on the cross-section of the joints was calculated by using ABAQUS numerical simulation software. The observation results on the cross-section of the joints show a nugget formed at the interface between the rivet tip and steel of lower plate. The maximum tensile shear load of the joints reached 5.82 kN at the welding current of 26 kA. This study reveals that the bearing interface of the resistance element welded joint between aluminium alloy and mild steel is like-to-like interface of aluminium alloy which strengthens the joint.

Long Cycle Life and High‐Rate Sodium Metal Batteries Enabled by an Active/Inactive Co‐Sn alloy Interface

AbstractSodium‐metal batteries (SMBs) are considered as a promising route to realize a high energy density battery, showing potential for applications in large‐scale energy storage. However, the cycling stability and reversibility of the Na‐metal anode suffer from significant challenges because of the growth of Na dendrites. This study reports an active/inactive Co‐Sn alloy interface to suppress the growth of Na dendrites under harsh test conditions. In this interface, Sn provides abundant nucleation sites and Co plays a synergistic role in alleviating volume variation of Sn nanoparticles and increasing the interaction between Na and substrate, significantly promoting the uniform Na deposition and preventing the Na plating from the root of the deposited Na. Under High‐current‐density (12 mA cm−2) with a high depth of discharge (DOD, 66.67%), Na||Na can achieve stable cycling for over 4200 h at 4 mA h cm−2. When paired with a high‐loading NaTi2(PO4)3 cathode (10 mg cm−2), SMB delivers an excellent performance (800 cycles) at a negative‐to‐positive electrode capacity (N/P) ratio up to 2.