Al Substrate Research Articles

Tunning solvation structure in non-flammable, localized high-concentration electrolytes with enhanced stability towards all aluminum substrate-based K batteries

Although metallic potassium or graphite anode with low redox potentials are desirable for potassium-ion batteries (PIBs), the severe capacity decay caused by consecutive reduction reactions on the aggressively reactive anode surface is inevitable because of the scarcity of an effective passivation layer. Additionally, the development of PIBs faces potential safety hazards due to the usage of reactive anodes with flammable electrolytes. Herein, a fire-retardant localized high-concentration electrolyte (LHCE) is formulated by adding a low-polarity co-solvent of highly fluorinated ether into the concentrated potassium bis(fluorosulfonyl)imide/trimethyl phosphate. A unique electrolyte solvation environment with the enhanced anion-cation interaction in an LHCE facilitates a durable anion-derived solid electrolyte interphase (SEI) with self-accelerated interfacial kinetics and minimizes the SEI dissolution compared to the conventional carbonate-based electrolyte. Consequently, the unmodified Al substrate could sustain stable potassium metal cycling above 3400 h (over 800 cycles) with high reversibility (98%), and the graphite anode retains prolonged cyclic stability (over 300 cycles) with a high reversible capacity (257.6 mAh g−1) and capacity retention (92.6 % at 0.2 C). Meanwhile, Al corrosion at high voltage is significantly suppressed, and the electrochemical window is extended due to less free solvents in an LHCE, enabling good electrolyte compatibility with high-voltage cathodes. Coupling non-flammable solvents and the concept of LHCE could facilitate a better understanding of electrolyte chemistry and offer more opportunities to use K or graphite anode for all Al substrate-based PIBs highlighted with high performance and superb safety.

Effect of Ag buffer layer thickness on the microstructure and hardness distribution of Cu alloy coating on Al substrate

The alloy coating is commonly used to enhance the hardness and wear resistance of Al substrate. However, the coating always cracks because of the brittle intermetallic compound (IMC) and thermal stress. In this investigation, the Ag buffer layer was employed to fabricate the crack-free Cu alloy coating. The effect of thickness of the Ag buffer on the phase transformation and hardness of Cu alloy coating was systematically investigated. The results showed that a thinner Ag buffer contributed to the dissolution of more Al and less Ag in the Cu alloy coating due to the dissolving of high-Al region of Ag buffer layer. A lower content of Ag in the Cu alloy coating brought more primary Cu-rich phase. The high Al in the Cu alloy coating contributed to the formation of β phase. During cooling stage, the β phase transformed into β′ phase through martensitic transformation. The more fine-grained β′ phase contributed to a higher hardness of 310 HV of the Cu alloy coating on the Ag buffer layer with a thickness of 450 μm. The thicker buffer layer contributed to the coating with less Al and more Ag. The Cu alloy coating exhibited a microstructure with more eutectic phase. The primary Cu-rich phase became Cu solid solution due to the lower Al concentration. The coarse-grained primary Cu solid solution and low-hardness eutectic phase contributed to the low hardness of 275 HV.

Improved optical and mechanical characteristics of multilayered Cu/TiON/CrO2 coating via heat treatment for solar absorbing applications

In the last few decades, growing interest has been shown in the development of new solar selective coatings based on transition metal nitride and/or oxinitride for solar absorbing applications. Solar thermal collectors are well thought out to be the most effective process of converting and harvesting solar radiation. In this investigation, Cu/TiON/CrO2 multilayered solar selective absorber coatings have been coated onto Al substrates using the dip-coating process followed by an annealing process at (400, 450, 500, 550, and 600 °C. The XRD analysis showed excellent crystalline quality for the prepared thin films along with enhanced surface features as proved by FESEM images, and the grains are in the range of (27–81) nm. The optical investigations revealed that the film annealed at 600 °C exhibits improved solar absorptance, thermal emittance, and solar selectivity of ~ (90.7 %), (5.8 %) and 15.6, respectively. Also, the highest values of hardness ~ (26.8 GPa) and Young’s modulus ~ (250 GPa) were assigned for the film annealed at the highest temperature. Calculated optical band gaps of fabricated thin multilayered Cu/TiON/CrO2 films were found to be in the range of (1.8 – 2.10) eV.

Disentangling Origins of Adhesive Bonding at Interfaces between Epoxy/Amine Adhesive and Aluminum.

Joining metals by adhesive bonding is essential in widespread fields such as mobility, dentistry, and electronics. Although adhesive technology has grown since the 1920s, the roles of interfacial phenomena in adhesive bonding are still elusive, which hampers the on-demand selection of surface treatment and adhesive types. In the present study, we clarified how chemical interactions and mechanical interlocking governed adhesive bonding by evaluating adhesion properties at the interfaces between epoxy/amine adhesive and two kinds of Al adherends: a flat aluminum hydroxide (AlxOyHz) and technical Al plate with roughness. Spectroscopic and microscopical data demonstrate that the protonation of the amino groups in an amine hardener converts Al(OH)3 on the AlxOyHz surface to AlO(OH). The interfacial protonation results in an interfacial dipole layer with positive charges on the adhesive side, whose electrostatic interaction increases the interfacial fracture energy. The double cantilever beam tests for the flat AlxOyHz and technical Al substrates clarify that the mechanical interlocking originating from the surface roughness further increases the fracture energy. This study disentangles the roles of the chemical interactions and mechanical interlocking occurring at the epoxy adhesive/Al interface in the adhesion mechanism.

Microstructural evolution and properties of Ti/Al clad plate fabricated by vacuum rolling and heat treatment

Ti/Al clad plate is a highly promising material due to its low cost, lightweight nature, high strength, and excellent corrosion resistance. However, the deformation coordination between Ti and Al is very poor, and both metals easily are oxidated, resulting in a weak interfacial bonding. In this study, Ti/Al clad plate was fabricated by vacuum rolling, obtaining a clear interface without oxidation and compound. The as-rolled Ti/Al clad plate had a shear strength of 76 MPa with the fracture being at the Al substrate due to the solution of Mg2Si precipitates in the Al substrate during rolling. As a result, the solution and aging is necessary to enhance interfacial bonding. There were fine and dispersed Mg2Si precipitates in the as-treated Al substrate, and an (Al, Si)3Ti layer with ∼300 nm thickness appeared at the interface. Besides, the interfacial shear strength was up to 140 MPa, and the fracture still was at the Al side. The as-treated clad plate had an elongation of 33.5% which exceeded that of 25.8% calculated by the mixed rule. Obviously, the thin (Al, Si)3Ti layer is helpful to improve interfacial shear strength and plasticity of the Ti/Al clad plate.

Interphases developed by interfacial reactions in polypropylene-aluminum joints unveiled by local thermomechanical analysis

Blending of maleic anhydride-grafted PP (PPgMA) into isotactic PP (iPP) has been discovered to improve its bonding strength with aluminum (Al) significantly. The optimal bonding performance is achieved with a 20 wt% of PPgMA, whereas pure PPgMA fails to adhere to Al. The results suggested that the chemical reaction between MA and the Al surface alone does not directly account for the bonding properties. To investigate the interfacial phenomena between iPP/PPgMA blends and the Al substrate, we employed local thermomechanical analysis using NanoTA. Remarkable variations in the thermomechanical response were obtained near the Al/PP interface compared to the bulk region and even the surface. The interphase, located approximately 10 µm from the Al/PP interface towards the bulk of PP, was identified through these analyses. Combining the findings from NanoTA, Differential Scanning Calorimetry (DSC), and scanning electron transmission electron microscopy (STEM) revealed that the chemical interaction between PPgMA and the Al surface triggers the formation of a wide interphase through the phase separation of iPP and PPgMA. Importantly, the interfacial chemical reaction does not directly enhance the bonding strength; rather, it generates the interphase, which plays a critical role in bonding strength.

Substrate thermal expansion coefficient effect on cracks induced by the high-heat treatment of electroplated Ni-P films for power devices

Automotive power semiconductors are required not to fail at high-temperature mounting (∼400 °C), and a structural design that prevents defects as well as cracks is essential. In this study, we focused on the thermal expansion coefficient of medium-phosphorus Ni films (P content: 8–9 wt%), which are commonly used for soldering or wire-bonding, with the substrates on which they are electroplated to investigate the effects of high-temperature heating on cracks induced in the Ni films. The Ni-P films were deposited on Al, Cu, Ni, and Fe substrates via electroplating technique using a Watts bath containing phosphorous acid. By heating to approximately 360 °C, the Ni-P film shrank because of the phase transition to a phosphorus compound mainly composed of Ni3P. As a result of the Ni film indentation test after heating to 400 °C, cracks were induced in the Ni film on the Cu substrate but not on the Ni substrate. The thermal expansion coefficients of the Cu and Ni substrates at approximately 360 °C were 17.4 and 14.8 µm m−1 °C−1, respectively; suggesting that the residual stress at the interface between the Ni film and the substrate affects cracking.

Electrodeposition and characterization of poly-aniline-Bi-Te-Se-Sb thin films with thermoelectric properties

Polyaniline-Bi-Sb-Te-Se thin films have been prepared by electrodeposition and electrochemical reaction method in different potentials and different concentrations of PANI: (Bi (NO3)3·5H2O), H2SeO3, K2TeO3 and Sb2O3 on Al substrate from nitric acid solution at room temperature. The structure and morphology of thin films were investigated by Fourier-transform infrared (FTIR), X-ray diffractometer (XRD), field emission scanning electron microscope (FE-SEM), and energy dispersive X-ray analysis (EDS) instruments. In addition, the thermoelectric power, resistivity, maximum power, and electrical conductivity of the thin films were evaluated. The results showed that an overall increase in voltage resulted in decreasing in the grain size and increasing in the dopant concentration. Furthermore, the coating morphology changed as the polyaniline precipitated, and nanoparticles were more uniformly distributed in the polymer coating via the increase in the voltage. Observations showed that the thin films were n-type semiconductors. Also, results showed that thermoelectric power increased by applied potential and temperature. It has been found that the chemical composition had a particular influence on the thermoelectric properties, which in comparison with previous works, at a similar temperature, a slight change in the chemical compound improved the thermoelectric properties by ∼ 65 percent.

Grain size and hardness: Key parameters for enhancing the chemo-mechanical stability of lithiated aluminum foil anodes

Aluminum (Al) has gained attention as a potential anode material for lithium-ion batteries (LIBs) due to several advantageous properties such as a relatively low volume expansion of approximately 97% during lithiation, a large charge capacity of 993 mAh/g, a low potential of 0.36 V vs. Li/Li+, high electronic conductivity, and its abundance in the Earth's crust. Furthermore, Al is readily available as foil, eliminating the need for binders, conductive additives, and expensive copper (Cu) current collectors. However, one of the challenges associated with Al as a LIB anode is the mechanical cracking of the lithiated β-LiAl phase, leading to rapid capacity fading. This paper introduces an effective strategy to address this issue by suppressing plastic deformation and pulverization of the Al anode during the lithiation process through grain refinement and strengthening of aluminum foil. The study demonstrates that cold-rolled low-purity (99.5%) purity Al foil anode exhibits higher resistance against plastic deformation during lithiation compared to cold-rolled high-purity (99.99%) Al foil. The superior chemo-mechanical stability of the cold-rolled 99.5% Al foil can be attributed to its higher hardness (90 Hv) and smaller grain size (1.7 µm) in comparison to the cold-rolled 99.99% Al foil (30 Hv and 73 µm). These microstructural and mechanical features play a key role in maintaining high chemo-mechanical stability in facing significant volumetric expansion during the phase transformation from Al to β-LiAl, while also facilitating the formation of a uniform lamellar β-LiAl layer on the Al substrate. This paper also presents a model that establishes a relationship between chronoamperometric current and plastic strain, enabling real-time estimation of invisible strain by monitoring the current during the lithiation process. This approach provides a means to assess the structural integrity of the anode during battery operation.

DFT Study of Cl− Ingress into Organic Self-Assembled Monolayers on Aluminum

We address the mechanism by which organic layers on aluminum substrate hinder the penetration of Cl− toward the metal substrate. Localized corrosion by chlorides on Al and its alloys is a major problem, and organic molecules that form self-assembled monolayers on metal substrates may provide efficient corrosion protection. In one of our previous works, we established experimentally that long-chain n-alkyl carboxylic acids form protective layers against Cl− corrosion on Al substrates. In a different work, we identified, using implicit models of the organic layer and metal substrate, two essential effects by which organic layers hinder the penetration of Cl− ions toward the metal substrate. The first effect is due to the inferior solvation of ions in the organic layer compared to that in an aqueous solvent. The second effect is due to the electric field at the electrochemical interface, and the extent to which it affects the penetration of Cl− depends on the electrode potential and the thickness of the organic layer. Both effects are related to a low dielectric constant of the self-assembled monolayer. In the present study, we continue our investigation and explicitly model the organic monolayer and Al substrate using density-functional-theory calculations. To this end, we consider organic monolayers consisting of either dodecanoic- or hexanoic-acid molecules. Current calculations confirm the findings of the simplified implicit models, i.e. the energy barrier for the Cl− penetration increases with the thickness of the organic monolayer and with Cl− concentration in the monolayer. Furthermore, we propose a new mechanism by which Cl− penetrates the organic monolayer. Due to the considerably inferior solvation of Cl− in the organic layer compared to that in water, calculations suggest that it is energetically easier to locally “open” the organic monolayer by creating a hole large enough to accommodate water molecules and Cl−. The presence of water molecules ensures a stronger Cl− solvation and a better electrostatic screening between anions. While the energy barrier for the Cl− penetration via the local “opening” mechanism is suggested to be smaller than for the penetration of Cl− into dense homogeneous organic monolayer, it is still significant enough to pose a considerable kinetic barrier for the penetration of Cl− from the aqueous solution into the organic monolayer at room temperature.

The effect of advanced electrodeposited Ni-P-Cu coatings obtained with scrap cu plates on the tribological performance of Al powder metallurgy products

With the increasing demand for even higher levels of wear resistance in various applications, researchers and manufacturers have been working on developing enhanced coatings for Al to enhance its wear properties even further. The aim of this research was to investigate the impact of electrodeposited Ni-P-Cu coatings derived from scrap copper, as well as coatings of pure NiP, comparatively, on the wear resistance of Al samples. The study involved a detailed examination of the effect of these coatings on the wear properties of Al, and the findings were analysed in depth. In this context, the relationship between the morphology, phase analysis, hardness and wear performance of the obtained coatings has been revealed in detail. In Al substrate materials, the adhesive wear mechanism is the primary mechanism, whereas in NiP and Ni-P-Cu coatings, the abrasive wear mechanism is more dominant due to the presence of a hard coating layers. In Ni-P-Cu coatings, the wear performance was increased by increasing the hardness of the coating despite the amorphous microstructure thanks to the Cu obtained from scrap Cu. At the end of the sliding distance of 100 m, it was determined that the wear resistance of Al samples increased by about 60 times thanks to Ni-P-Cu coatings. Specifically, the current work focused on the potential benefits of these coatings in enhancing the abrasion resistance of Al, which is a crucial aspect of its performance in many industrial applications. By comparing the wear properties of coated and uncoated Al samples, the durability and longevity of this material was highly improved by the role of developed Ni-P-Cu coatings including Cu ions from scraps.

Lithium salts as active corrosion inhibitors for aluminum substrates

As an effort to replace carcinogenic chromate from protective coatings, researchers are continuously searching and proposing new non-toxic chemicals sharing similar properties: leachable, responsive, and film-forming. Lithium (Li), in the form of either a salt additive in coatings or alloyed with aluminum (Al), is observed to be able to form insoluble protective layers and thus reduce the corrosion rate of the Al substrates. The protective film formed is often composed of Li, Al, carbonate (CO3), hydroxide (OH) etc., sharing similar structure to a layered double hydroxide (LDH) as indicated by several mechanistic studies. The successful formation of the irreversible/insoluble protective film requires oxygen, correct pH, and the right combination of available ion species. In this study, electrochemical impedance spectroscopy (EIS) results show that these leachable inhibitor coatings yield poor barrier properties before and after artificial weathering. Scanning electron microscopy pictures show the growth of an inorganic layer between the coating and aluminum substrate, indicative of the formation of a layered double hydroxide (LDH) structure. Current mapping generated by scanning vibrating electrode technique (SVET) indicates that aerated lithium salt solutions can cause pitting corrosion over bare aluminum, while organic coatings pigmented with lithium were able to keep the surface relatively passive, with and without the presence of a defect. An anodic shift of the surface of the organic coatings pigmented with lithium containing a defect is seen while keeping the surface relatively passive, indicating anodic passivation of the metal surface.

Selective alloying of pure aluminum with varying amounts of magnesium using friction stir processing for improved mechanical and corrosion-resistant properties

This study investigates the effects of adding different amounts of Mg to the surface of pure Al substrate using friction stir processing (FSP) technique to prepare Al–Mg solid solutions. For this purpose, machined grooves on the surface of the pure Al plates were filled by bulk Mg blocks and FSPed to form Al–Mg solid solution layers with ∼2.0, 4.5, and 33.9 at.% Mg. The chemical composition, microstructure, and surface Volta potential of the surface alloyed layers were studied by SEM/EDS, XRD, and SKPFM, respectively. The results revealed that incorporating Mg into the Al substrate causes a considerable refinement of the microstructure, resulting in a significant increase in Vickers hardness number from 25 to 208.4 HV (∼734% increase). As the Mg content in the alloyed layer increased, a transition from a single-phase solid solution structure to a dual-phase structure was observed. Based on the potentiodynamic polarization results, it is evident that the corrosion resistance of the single-phase alloyed layer can match that of marine-grade aluminum alloys.

Computationally developed acrylated epoxidized methyl ester based pressure-sensitive adhesives

Healthcare sector is increasingly demanding pressure-sensitive adhesives (PSAs) to be bio-sourced and biodegradable to replace petro-based PSAs, which are neither renewable nor sustainable. This investigation employs MD simulations to develop bio-based PSAs by replacing low Tg monomers such as 2-ethylhexyl acrylate partially and fully with acrylated epoxidized methyl ester (AEME). The simulation procedures used in this study were verified by comparing specific properties with published literature. The glass transition temperatures of all developed systems show insignificant differences and are well below application as desirable for developing PSA products. Also, these values closely match Fox equation estimates and are in good accord with experimental values. Surface characteristics like surface energy and interfacial adhesion with Al substrate have been predicted. A ∼79 % increment in surface energy with AEME content ensures good substrate wettability and thermodynamic work of adhesion. The interaction energy with Al substrate has been increased by ∼365 % with addition of AEME reflecting improved adhesion strength and enhanced tackiness of the PSA copolymer. AEME provides polar groups like acrylate and hydroxyl groups, which helps improve adhesion strength. The polar groups associated with AEME and increased crosslinking density enhanced mechanical properties of developed PSA systems. This computational research lays the path for developing innovative bio-based PSAs used in adhesive bandages and transdermal patches.

Electrical properties of Al-Si surface composites through surface mechanical alloying on severe plastic deformed Al substrates

Surface mechanical alloying ‘SMA’ with Si powder on Al was used to achieve surface composite with improved dielectric properties compared with coarse-grained and annealed Al composites. Measured Dielectric constant ε', dielectric loss ε" and Capacitance CμF versus increasing frequencies (105-108 Hz) exhibit a frequency dependent behavior of composite containing Al-Si solid solution in a voltage range from 0.1 to 0.5 V at room temperature. Found that an increase of Si content in surface composite results in ε, tan δ & C increase due to formed solid solutions between Al & Si after SMA on pre-severe plastic deformed Al substrates. Concluding the important role played by the severe plastic deformed microstructure of Al electrode in controlling dielectric properties of Al surface containing Al-Si composite.

Preparation and cooling performance analysis of double-layer radiative cooling hybrid coatings with TiO2/SiO2/Si3N4 micron particles

Passive daytime radiative cooling is achieved by radiating heat into outer space through electromagnetic waves without energy consumption. A scalable double-layer coating with a mixture of TiO2, SiO2, and Si3N4 micron particles for radiative cooling is proposed in this study. The finite-difference time-domain algorithm is used to analyze the influence of particle size and coating thickness on radiative cooling performance. The results of the simulation show that the particle size of 3 μm can give the best cooling performance, and the coating thickness should be above 25 μm for SiO2 coating. Meanwhile, the mixture of SiO2 and Si3N4 significantly improves the overall emissivity. Through sample preparation and characterization, the mixture coating with a 1:1 ratio addition on an Al substrate exhibits high reflectivity with a value of 87.6% in the solar spectrum, and an average emissivity of 92% in the infrared region (2.5 μm–15 μm), which can be attributed to the synergy among the optical properties of the material. Both coatings can theoretically be cooled by about 8 °C during the day and about 21 °C at nighttime with h c = 4 W⋅m−2⋅K−1. Furthermore, even considering the significant conduction and convection exchanges, the cooling effect persists. Outdoor experimental results show that the temperature of the double-layer radiative cooling coating is always lower than the ambient temperature under direct sunlight during the day, and can be cooled by about 5 °C on average, while lower than the temperature of the aluminum film by almost 12 °C.

Nanoporous Membrane Electrodes with an Ordered Array of Hollow Giant Carbon Nanotubes

AbstractThis study proposes a next‐generation model membrane electrode for fundamental electrochemical research of amorphous‐based porous carbon materials. This novel electrode is fabricated by the uniform carbon coating of anodic aluminum oxide formed on an Al substrate and free from a barrier layer. The conformally carbon‐coated layer forms vertically aligned giant carbon nanotubes, and their walls comprise low‐crystalline stacked graphene sheets. The diameter and the length of the nanopores can be tuned over a broad range of between 10 to 200 nm and 2 to 90 µm, respectively. Moreover, unlike composite electrodes made from other ordered nanoporous carbons, this model electrode exhibits an absence of inter‐particle spacing and hence no contact resistance between particles. Thus, this model electrode provides representative nanopores of low‐crystalline carbon materials. An atomic‐scale structural model of the low‐crystalline carbon walls is built with the aid of an in‐house temperature‐programmed desorption system to enable theoretical simulations to be performed. Using this model electrode, the electrical conductivity of low‐crystalline carbon walls and mass transportation in an electric double‐layer system are elucidated. This representative model electrode is expected to help clarify the complex electrochemical processes in porous carbon electrodes.

Experimental and theoretical studies on the inhibitory potential of Lippia javanica leaf extract for aluminium corrosion in 1M HCl medium

Electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), and gravimetric analysis techniques were used to evaluate the ability of Lippia javanica leaf extract to inhibit aluminium (Al) corrosion in 1 M HCl solution. The formation of the protective film was confirmed using Ultraviolet-visible spectroscopy (UV–Vis), Fourier transform-infrared spectroscopy (FTIR) and contact angle studies. According to EIS, the presence of L. javanica extract in the acidic solution decreased the corrosion current density (icorr) and the double-layer capacitance (Cdl) due to the formation of a protective adsorption layer on the Al surface. PDP curves revealed anodic polarization passivation of the Al substrate, a well-known property of a highly entropic alloy like Al. Gravimetric results showed that the maximum protective efficacy of the L. javanica extract was 91.89% when the optimal concentration of the extract was 800 ppm. The contact angle increased to 123° in the presence of ALJPE, indicating the hydrophobic nature of the Al surface due to the formation of a protective film. The FTIR spectra revealed the involvement of C=O, C=C, O–H, =C–O–C, S=O, and C–H during the adsorption process, leading to the formation of ALJPE–Al3+ protective complexes. It was discovered that the adsorption mechanism of the extract on the Al surface follows the Langmuir adsorption isotherm description process. Using density functional theory (DFT), different dsorption positions were studied, finding that verbascoside preferentially binds to the Al(111) surface via the phenylethanoid group, with the oxygen atom close to the Al surface, leading to a binding energy of 114.620 kcal/mol.

Impact of spray angle and particle velocity in cold sprayed IN718 coatings

Cold spray (CS) deposition has potential applications in repair technology or additive manufacturing due to its ability to operate at low temperatures, achieve high deposition rates, and produce thick, dense coatings. For adoption of CS in repair applications, it is crucial to evaluate the influence of spray angles since geometry of repair zones are typically complex and non-flat. In this work, we investigated the influence of spray angles and particle velocities on the cold spray deposition of Inconel 718 (IN718) powder particles using N2 as propellant gas. Three oblique spray angles including 50, 60 and 70° were compared with the 90° normal spray angle for cold spray deposition of IN718 powders on Al6061 substrate. Three sets of cold spray parameters at each spray angle, giving particle velocities from 820 to 920 m/s were employed to study their effect on the coating properties. Particle velocity was found to have greater impact on coating porosity compared to spray angle. Coating with lowest porosity and lowest surface roughness but highest compressive surface residual stress was achieved with deposition at lowest spray angle (50°) and highest particle velocity (920 m/s). Changing the spray angle has greater influence on the deposition efficiency, with thickest coating observed at normal spray angle of 90° across all three cold spray conditions. Finite element method (FEM) simulations were also performed to understand the influence of powder and substrate temperatures on critical angles for bonding. The simulation results suggest that elevating the powder temperature is likely to cause a slight increase in the critical bonding angle.

Microstructural evolutions and mechanical characteristics of roll-bonding Mg/Al clad plate regulated by cold spraying micron particle interlayer

A new process of “cold spraying interlayer + roll-bonding” (CSIR) was put forward for the preparation of Mg/Al clad plates. First, the micron Ni and Al powders (including some Zn particles) were cold sprayed to form an ultrathin coating on Al or Mg substrate slabs. Then roll-bonding was performed at 400 °C. The influence of cold sprayed coating on slab surfaces, interfacial microstructures, texture evolutions, mechanical properties and the related mechanism were systematically investigated. The results show that the average shear strength of the as-rolled Mg/Al clad plate assisted by cold spraying Al and Ni micron powders interlayer on the substrate slabs was nearly twice (35.58 MPa) than that of conventional rolling under the same conditions (single pass, reduction ratio was 35%). For as-rolled Mg/Al clad plates, almost no reaction diffusion layers are generated, and the mechanical interlocking between cold sprayed coatings and substrate slabs is the main mechanism for improving the shear strength. The interface between the Al coating and the Ni coating is weakest of the as-rolled Mg/Al clad plates. As the reduction rate increases from 27.5% to 47.5%, the function of the mechanical interlocking of cold sprayed coatings will first increase and then weaken. After annealing at 400 °C for 1 h, the interface between the Al coating and the Mg substrate slab will form thick mixed brittle intermetallic compounds, including Al3Mg2, Mg17Al12, MgZn2 and AlMg4Zn11, and cause local gaps, holes, and cracks around the Zn-rich Ni coating. The fracture path after annealing starts from the vicinity of the defective Ni particles, and eventually enlarges along the mixed intermetallic compounds layer between the Al coating and the Mg substrate slab. The research indicates that the CSIR process has great potential in cooperating the metallurgical bonding with the mechanical interlocking of clad plates.