Diffusion Of Elements Research Articles

New insights into the influencing mechanism of ultrasonic vibration on interface of Al/Mg bimetal composites by compound casting using simulation calculation and experimental verification

In this work, the numerical simulation of acoustic pressure distribution in ultrasonic vibration-assisted compound casting of Al/Mg bimetal composites was conducted. Relevant experimental verification was also performed to understand the influence of ultrasonic vibration treatment (UVT) on the interfacial microstructures and mechanical properties of the Al/Mg bimetal composites. Results revealed that the acoustic pressure distributions in the AZ91D melt were related to the vibration frequencies. The effective cavitation area at the Al/Mg interface reached the maximum percentage of 95.6 %, with the ultrasonic frequency of 20 kHz. The experimental results found that the Al/Mg interface without UVT was composed of Al–Mg intermetallic compounds (IMCs, i.e., Al3Mg2 and Al12Mg17) layer and eutectic layer. The oxide film and gas gap were existed between the two layers. The Mg2Si particles were gathered at the IMCs layer. The interfacial grains were coarse and their growth was directional. With UVT, the effective cavitation was occurred at the Al/Mg interface. The oxide film was broken, and the gas gap was eliminated. The interfacial microstructures were significantly refined. Due to the accelerated elemental diffusion and solute transfer by UVT, a more homogeneous Al/Mg interface was obtained. The Mg2Si particles were refined and formed at the eutectic layer. The microhardness mismatch of the IMCs layer and eutectic layer was decreased by UVT. The shear strength of the Al/Mg bimetal composites with UVT was enhanced to 62.2 MPa, which increased by 62.8 %, compared with that without UVT.

Effects of thermal exposure on microstructure deformation and evolution of shot peened nickel-based single crystal superalloy

Microstructure deformation and thermally activated microstructural evolution of nickel-based single crystal (NBSC) superalloy subjected to shot peening (SP) were investigated. SP induced high-density dislocations and activated the octahedral slip system {111} 〈110〉 of NBSC superalloy. Under 0.25 mmA SP intensity, there appeared a severely deformed layer with a depth of 2.5–3.0 μm beneath the surface. High SP intensity resulted in rougher surface morphology, more dense slip bands, deeper cold work layer and larger mean geometrically necessary dislocation (GND) density. However, the deformed microstructure was thermodynamically unstable. Dislocation annihilation and rearrangement were the main thermally activated mechanism of microstructural evolution, and high temperature promoted dislocation movement and consumption. Under 0.25 mmA SP intensity after 24 h thermal exposure, GND density decreased from 4.86 × 1014 m−2 to 2.72 × 1014 m−2, and the depth of cold work layer decreased from 67 μm to 62 μm. In addition, SP treatment provided rapid diffusion channels for alloy elements, while thermal exposure further aggravated element diffusion.

Interfacial bonding mechanism and mechanical properties of Cu-Ni-Si/1010 steel bimetallic laminated composites prepared by continuous solid/liquid bonding

The Cu-Ni-Si/1010 steel bimetallic laminated composites (BLCs) were prepared by continuous solid/liquid bonding, and the microstructure, mechanical properties and interfacial bonding mechanism were investigated. The results show that the microstucture of Cu-Ni-Si mainly consists of α-Cu, and a small quantity of Ni-Si rich phases which distribute at the grain boundaries. Meanwhile, the microstucture of 1010 steel is composed of ferrite (F), pearlite (P), and a small amount of bainite (B). A flat and well-bonded interface is formed between two layers due to the diffusion of elements. The diffusion layer is identified as the Fe based solid solution containing Ni and Si by TEM. The interfacial bonding mechanism is revealed using Fick's second law and thermodynamic methods. The results show that the diffusion coefficients of Ni and Si in Fe are higher than those of in Cu, and the molar Gibbs free energies of mixing (GmixM) of Fe-Ni and Fe-Si are lower than those of Cu-Ni and Cu-Si, indicating that Ni and Si tend to diffuse to Fe. The ultimate tensile strength, yield strength and elongation of Cu-Ni-Si/1010 steel BLC are 378 MPa, 233 MPa and 25.4 %, respectively, which lie between those of individual Cu-Ni-Si and 1010 steel. The tensile shear results show that the interface is always well bonded, and no cracks are found at the interface during the deformation. The fracture of the Cu-Ni-Si/1010 steel BLC occurs at the Cu-Ni-Si side, suggesting that the bonding strength is larger than that of the Cu-Ni-Si.

Effect of continuous gradient Al on high-temperature oxidation of Ni-Cr-Co based superalloys via a high-throughput method

This study focuses on the effect of the main antioxidation element Al on the high-temperature oxidation resistance of Ni-Cr-Co based superalloys. A novel “3D printing-high temperature diffusion” high-throughput method was used to accurately determine the critical Al content to form continuous Al2O3 film. Results show that Al2O3 film significantly affects the element diffusion process during oxidation, and the critical Al content to form continuous Al2O3 film is 0.8 wt%. This conclusion was further confirmed by the corresponding discrete samples. It was also found that Ni-Cr-Co based superalloys exhibit “oxidation weight loss” and “Kp-antioxidation positive correlation” phenomena in high humidity condition.

Effect of sintering temperature on the properties of titanium matrix composites reinforced with Al0·5CoCrFeNi high-entropy alloy particles

In this study, the organization and mechanical properties of the composites were analyzed at different sintering temperatures, and it was found that the local high-temperature phenomenon of discharge plasma sintering led to rapid melting and element diffusion at the junction of the high-entropy alloy particles and the Ti matrix, resulting in the formation of the interfacial layer. The increase in sintering temperature promoted close bonding between particles and element diffusion, caused lattice distortion and new phase formation, and increased the thickness of the interface layer and precipitated phase at the grain boundary. Most of the high-entropy alloy particles were dissolved when the sintering temperature reached 1050 °C. The composites were characterized by a high sintering temperature. The comprehensive mechanical properties of the composites first increased and then decreased when the sintering temperature increased, and they were optimized at 850 °C. The nanoindentation results show that the increase in sintering temperature leads to a decrease in the hardness of the high-entropy alloy particles, an increase in the hardness of the titanium matrix, and a higher hardness of the interfacial layer than that of the high-entropy alloy particles and the titanium matrix.

Influence of High-Temperature Deformation on the Dissolution of δ-Ferrite in Stainless Steels

The dissolution behavior of δ-ferrite in two commercial stainless steels, 15-5PH and M-154, was studied. In this work, a new approach combining hot deformation and additional post-treatment was investigated and compared with conventional annealing heat treatments for the dissolution of δ-ferrite. The results showed the acceleration in the dissolution of δ-ferrite using the new methodology. Samples from each steel were subjected to conventional annealing heat treatments at 1000 °C and 1150 °C, with soaking times of 1, 2, and 3 h. A second set of samples was subjected to hot compression experiments at 900 °C, under different strain rates, followed by post-processing heat treatments at 1000 °C and 1150 °C, while keeping the holding time constant for 10 min. Advanced microstructural characterization techniques such as Scanning Electron Microscopy (SEM), and Electron Probe Micro-Analysis (EPMA) were employed to investigate δ-ferrite dissolution in terms of changes in area fraction and chemical composition. The results indicated a strong correlation between the dissolution behavior of δ-ferrite and the processing parameters. In addition, thermodynamic calculations using Thermo-Calc software (version 2021.2.87071-368) were used to assess the diffusion of elements during the dissolution of δ-ferrite as a function of temperature and time.

Coarsening transitional kinetics of γ′ precipitates in a nickel-based single crystal superalloy during thermal exposure

The microstructural stability and coarsening kinetics of γ′ precipitates in a nickel-based single crystal superalloy (Ni-SX) were thoroughly investigated under various thermal exposure treatments. The evolutions of characteristic parameters including γ′ size, morphology, area fraction, and γ channel width were documented. Coarsening rate constants and particle size distributions (PSDs) were calculated and recorded based on measured precipitate sizes at temperatures ranging from 800 ℃ to 1100 ℃ and durations ranging from 100 h to 1010 h. The experimentally derived rate constants were compared with the calculated theoretical values from two mainstream models: matrix-controlled diffusion (LSW model) and interface-controlled diffusion (TIDC model). Notably, transitional coarsening kinetics of γ′ precipitates from the LSW model to the TIDC model was observed at high temperatures over time. Through a comprehensive consideration of key coarsening kinetics parameters such as elemental diffusivity, trans-interface diffusion coefficient, coarsening rate constant, γ/γ′ interfacial area, and solute mass transfer, the transformation of the coarsening kinetics from matrix-controlled diffusion to interface-controlled diffusion was quantitatively discussed. The emergence of the TIDC model as the dominant mechanism was attributed to relatively smaller solute mass transfer through the interface. Moreover, the degradation of γ/γ′ interfacial energy and interfacial area, coupled with the increase in solute diffusion coefficient in the matrix, facilitated the trans-interface diffusion to act as a limiting factor throughout the coarsening process.

Comparative Analysis of Water-Induced Response in 3D-Printed SCF/ABS Composites under Controlled Diffusion

Additive manufacturing (AM) or 3D-printing of fiber-reinforced composites (FRCs) has garnered significant interests for its versatility in creating intricate parts and rapid prototyping due to cost-effectiveness. Although short fiber-reinforced thermoplastic composites are challenging to manufacture, their mechanical properties can be easily tailored by adjusting fiber type, orientation, and volume fraction. However, void formation during printing is a key issue, impacting mechanical properties and facilitating water ingression, affecting long-term durability. This work studies water diffusion characteristics and the associated hydro-aging of 3D-printed short carbon fiber (SCF)/acrylonitrile butadiene styrene (ABS) composites with controlled water diffusion. Effects of material type (ABS and SCF/ABS), 3D-printing path (horizontal and vertical filament orientation), and diffusion surface (uni-directional and bi-directional diffusion) on water diffusion coefficient and maximum water absorption level are characterized to ensure the long-term durability of 3D-printed ABS and SCF/ABS composites. Baseline representative volume element-based finite element (RVE-FE) diffusion models were developed based on micro-computed tomography (micro-CT) image analysis to understand water diffusion characteristics. This work proves that the SCF/ABS composite is more resistive to hydro-aging than neat ABS due to the SCFs’ hydrophobic nature. SCF/ABS composites, while providing distinct advantages over pure ABS in terms of mechanical properties, could also be more effective against water environments.

Effect of annealing temperature on interfacial microstructure and tensile fracture behavior of titanium-steel clad plate

To ensure that the rolled composite plate has excellent processing properties. Annealing is an effective means of modulating organization and mechanical properties. In this study, annealing treatments at different temperatures were applied to the rolled titanium-steel clad plate. The evolution of the interfacial organization was observed using scanning electron microscopy. The strain distribution of the composite plate in the tensile process was investigated using a tensile experiment combined with the DIC method. The results indicate the presence of compounds such as TiC, Fe2Ti, and FeTi after hot rolling. As the annealing temperature increases, the thickness of the interlayer diffusion of elements between the two plates increases. The geometric dislocation generated between the grains after hot rolling is significantly improved after annealing treatment, and the geometric dislocation density decreases with the increase in annealing temperature. In the titanium layer, the titanium grains, after annealing at 550 °C and 600 °C, are in the recovery stage, and the amount of recrystallization does not change significantly. However, after annealing at 650 °C, the titanium grains are completely recrystallized, the grains are equiaxed, and the grain-to-grain anisotropy is eliminated. The sample annealed at 550 °C fractures almost simultaneously in the tensile test in the titanium layer and steel layer, with an elongation of 32.3% and a tensile strength of 477.1 MPa, showing the best comprehensive performance. Based on DIC strain curve analysis, The strain curve after annealing at 550 °C is smoother, the necking is relatively consistent, and it reaches a point of relatively consistent local strain instability.

Study on the Elemental Diffusion Distance of a Pure Nickel Layer Additively Manufactured on 316H Stainless Steel

Study on the Elemental Diffusion Distance of a Pure Nickel Layer Additively Manufactured on 316H Stainless Steel

Annealing activated substrate element diffusion and its influence on the microstructure and mechanical properties of CVD TiN/TiCN coatings

TiN/TiCN deposited by chemical vapor deposition (CVD) is widely used as hard coating system for cemented carbide cutting tools, typically under an Al2O3 top layer. During the deposition of the Al2O3 top layer, the underlying TiN and TiCN layers are exposed to high temperatures. Therefore, the present study focuses on the influence of this Al2O3 deposition step, which is mimicked by a vacuum-annealing treatment, on the microstructure and mechanical properties of the TiN/TiCN coating. By applying advanced characterization techniques such as scanning electron microscopy, scanning transmission electron microscopy, transmission Kikuchi diffraction, atom probe tomography, and micro-mechanical bending tests on both, as-deposited and annealed coatings, changes in the microstructure and mechanical properties were studied. It was found that W and Co diffusion occurs along the TiN and TiCN grain boundaries from the substrate into the coating. While the hardness, Young's modulus, and fracture toughness remained unaffected by the annealing treatment, a significant decrease of the fracture stress with increasing annealing time was observed. The present study provides a fundamental understanding of substrate element diffusion in CVD TiN/TiCN coatings deposited on cemented carbide substrates.

A grey-box model with neural ordinary differential equations for the slow voltage dynamics of lithium-ion batteries: Application to single-cell experiments

Lithium-ion batteries exhibit a complex, nonlinear and dynamic voltage behaviour. Modelling their slow dynamics is a challenge due to the multiple potential causes involved. We present here a neural equivalent circuit model for lithium-ion batteries including slow voltage dynamics. The model uses an equivalent circuit with voltage source, series resistor, and diffusion element. The series resistance is parameterized using neural networks. The diffusion element is based on a discretized form of Fickian diffusion, parameterized using a neural network and learnable parameters. It is flexible to represent not only Warburg behaviour, but also resistor-capacitor-type dynamics. Mathematically, the resulting model is given by a differential–algebraic equation system combining ordinary and neural differential equations. Therefore, the model combines concepts of both physical theory (white-box model) and artificial intelligence (black-box model) to a combined framework (grey-box model). We apply this approach to a lithium iron phosphate based lithium-ion battery cell. The experimental voltage behaviour during constant-current cycles as well as the dynamics during pulse tests are well reproduced by the model. Only at very high and very low states of charge the simulation significantly deviates from experiments, which might result from insufficient training data in these regions.

Interfacial reaction characteristics and mechanisms during dissimilar friction stir lap welding of pure copper and Al0.1CoCrFeNi alloy

In order to explore the weldability and widen the applicability of high entropy alloys (HEAs), dissimilar friction stir lap welding of pure copper and Al0.1CoCrFeNi alloy was investigated in this research. The results indicate that a sound dissimilar weld without tunnels and voids is produced, where a ∼20 μm thick interfacial layer is evident at the Cu-HEA interface. The lap joint is fractured at the upper Cu sheet rather than the lap surface during tensile shear test, suggesting an effective bonding of the dissimilar materials. The lap weld roughly consists of three layers along the plate thickness direction, i.e. welds of Cu, HEA and Cu-HEA interface, respectively. The interface of weld, which has experienced the most severe Cu-HEA interaction during welding, is characterized by uniformly distributed and highly recrystallized ultra-fine grains (∼0.79 μm). Meanwhile, intermetallic compounds particles (Al13Cr2 and Al13Co4) ranging in size of 150∼400 nm are generated at the fine grain boundaries. Fast diffusion of Al, Cr and Co elements and easy segregation of these elements during welding result in the formation of the particles. The sufficient DDRX and the pinning effect of particles are responsible for the formation of ultra-fine grains in the weld interface. The present study lays a theoretical foundation for the joining of conventional Cu and the multi-component HEA, which contributes to the improvement of HEA availability in the field of manufacturing industry.

Effect of NiMo diffusion barrier plating preparation on microstructure and properties of Bi2Te3/Cu joints

Bismuth telluride (Bi2Te3) thermoelectric devices play a significant role in recovering low-grade waste heat. While for Bi2Te3/Cu joints, excessive interfacial reaction and diffusion usually happens, which greatly degrades their properties. In this work, the novel NiMo diffusion barrier plating was prepared on Bi2Te2.7Se0.3 (n-BST) surface prior to the soldering process. The joint interfacial microstructure, shear strength, contact resistance and thermal stability were systematically investigated. The maximum shear strength increased from 7 MPa to 12 MPa with the joint contact resistance decreasing from 11.86 μΩ⋅cm2 to 3.27 μΩ⋅cm2 after NiMo plating preparation. These n-BST/Cu joints were then annealed for different durations to investigate the joint thermal stability. After annealing at 110 °C for 250 h, a thin BiTe + NiTe2 reaction layer formed instead of the initial SnTe reaction layer. The joint shear strength maintained 9 MPa (less than 2 MPa without NiMo plating) and the joint contact resistance was only 12.39 μΩ⋅cm2 (249.89 μΩ⋅cm2 without NiMo plating). This work indicates that NiMo plating is an effective elemental diffusion barrier for n-BST/Cu joints.

High temperature oxidation behavior of a Ni–Co-based superalloy

Oxidation behavior of a Ni–Co-based superalloy prepared by vacuum induction melting (VIM) plus electron beam smelting layered solidification technology (EBSL) and VIM plus electro slag remelting (ESR) at 1180 °C was investigated. The predominant oxides from the outer layer to the inner layer are TiO2, Cr2O3, (Al, Ti)-rich oxide and Al2O3, respectively. The (Al, Ti)-rich oxide is considered to be Al2Ti4O9, which is formed by TiO2 and Al2O3. At high temperature, the external oxides experienced significant spalling, particularly in ESR-alloy, which indicated that the EBSL-alloy is more preferable in terms of oxidation resistance. This can be attributed to the presence of finer grains in EBSL-alloy, which facilitates the diffusion of elements and promotes the rapid formation of oxidation scales on the surface of the alloy. Additionally, the presence of a TiO2 layer cover on Cr2O3 reduces the degree of spalling of oxides in EBSL-alloy.

Flame-retardant mechanism for platinum coating of nickel-based superalloy

This study presents a novel approach for enhancing combustion resistance of a nickel-based superalloy by the application of platinum coating. The combustion behaviors of Pt-coated samples were studied using the promoted-ignition combustion standard test at 7–25 MPa (≥ 99.5 % oxygen). In contrast to uncoated samples, the Pt-coated samples exhibit notable improvements in resistance to burning, as demonstrated by reduced combustion length and rate. The underlying mechanism can be ascribed to two factors. One notable effect of the Pt coating is the influence on diffusion and distribution of combustion elements. In particular, it impedes the oxidation and combustion of Al with the highest combustion heat. The second one is the comparatively lower heat released by the Pt-coated samples throughout the combustion process, as well as the substantial capacity to reduce the temperature at which combustion ceases. The aforementioned discoveries offer new perspectives on enhancing the compatibility of metal materials with oxygen.

Effect of diffusion of elements on microstructural, mechanical, and machining characteristics of Al7075/ZnAl4 functionally graded material with and without Ag and Pb interface

The current experimental work uses die casting, a liquid processing method, to create functionally graded material (FGM). To reduce the production of undesired intermetallic compounds, the FGM samples were created both with and without interfacing foil during the procedure. Mechanical properties including impact strength and microhardness were examined throughout the manufactured sample's cross-section. In addition, the interfacial bonding of FGM samples with and without an interacting foil was determined by estimating the shear strength. Analysis of the samples using X-ray diffraction (XRD) and scanning electron microscopy (SEM) reveals the existence of compounds in the sample as well as the diffusion of Al and Zn particles from one side to the other. Compared to the FGM without foil, it is observed that the diffusion rate at the interface is regulated when the foil is present. In addition, it was found that, in contrast to pb foil, the inclusion of Ag foil limited the rate at which particles could move from one side to the other. Additionally, machining investigations are carried out at varying depths on both sides of the sample in the direction of the interface with the assistance of electric discharge machining.

Microstructure and strengthening mechanism of TIG welded joint of AZ31 alloy based on FSP technique

Magnesium alloys, renowned for their outstanding properties, present promising applications within the realm of advanced manufacturing. Addressing the challenges of coarse grains and inferior properties in the fusion welding of magnesium alloys, a novel strengthening approach for fusion-welded joints is proposed in this study. This method employs fine, uniform, and dense grains as the matrix, with particle-reinforced structures serving as the strengthening backbone. By utilizing powder feeding in conjunction with fusion welding and friction stir processing, ideal microstructures were successfully fabricated, and the mechanisms influencing grain morphology and joint properties were explored. Following the strengthening treatment, the grain size of the magnesium alloy molten weld was reduced from 193.5 μm to 15.9 μm, resulting in a grain refinement efficacy of 91.8 %. Concurrently, the tensile strength was augmented by 70.2 MPa, and the elongation experienced a 136 % enhancement. The grain morphology, eutectic phase structure, texture strength, precipitated phase type and dislocation distribution at each processing stage of the welded joint were observed. Research shows that nano-enhanced particles adhere to the eutectic structure of grain boundaries, effectively inhibiting the diffusion of solute elements and significantly reducing the dendrite growth rate. It is the main mechanism by which reinforced particles lead to grain refinement. Discontinuous recrystallization during FSP treatment leads to grain refinement, work hardening and enhanced pinning of particles at grain boundaries, which are the main reasons for the strength improvement.

Formation and Migration Enthalpy from Elemental and Cooperative Diffusion in Lead Silicate Supercooled Liquid and Glass

Formation and Migration Enthalpy from Elemental and Cooperative Diffusion in Lead Silicate Supercooled Liquid and Glass

Effect of laser energy density on cracking susceptibility and wear resistance of laser-clad tribaloy T-800 coatings on DD5 single-crystal alloys

In order to enhance the wear resistance of DD5 single-crystal alloys, Tribaloy T-800 wear-resistant coatings were prepared on their surfaces using laser-cladding technology. This study examines the effect of laser energy density on the cracking susceptibility and wear resistance of laser-clad Tribaloy T-800 coatings on DD5 single-crystal alloys. Three distinct laser energy densities (η1=33 J/mm², η2=50 J/mm², η3=60 J/mm²) were applied to create the coatings. The results show that the microstructures of the T-800 laser-clad coatings mainly consist of primary, coarsened, and spheroidized Laves phases, as well as Co-based solid solution and eutectic structures. The phases include Co3Mo2Si phase (Laves phase) and face-centered cubic Co-based solid solution. However, increasing laser energy density enhanced elemental diffusion at the heterogeneous joining interface of the DD5 substrate/T-800 coating, leading to higher Ni content in the coating. This resulted in a reduction in the tendency and content of Mo-rich Laves phase formation respective contents of 53.2 %, 49.2 %, and 47.5 %. Moreover, the decrease in the difference between laser cladding temperature and initial temperature, ∆T, led to reduced thermal stress at the interface, σ, contributing to a decrease in cracking susceptibility (a), with corresponding values of 0.16184, 0.00034, and 0.00022. Thermal expansion coefficients of materials in the cracked region near the interface, measured according to the CALPHAD method, Jmatpro software, and average EDS elemental content data at the crack edge, surpassed those of the corresponding DD5 substrate. Consequently, cracks in the coatings originated from stretching at the interface, with paths tending to cross Laves phase particles in a cleavage mode. The average microhardness of the coatings decreased due to reduced Laves phase content, with values of 783.4 HV0.5, 741.7 HV0.5, and 708.2 HV0.5, respectively, while the fatigue wear of T-800 coatings increased due to exacerbated wear damage from cracking defects. Specifically, average COFs were 0.659, 0.583, and 0.506, with corresponding mass losses of 7.1 mg, 3.4 mg, and 2.9 mg, respectively. The wear mechanisms observed encompassed fatigue wear, abrasive wear, and oxidative wear.