Al Alloy Research Articles

Microstructure, Mechanical Behavior, and Tensile Fractography of Si3N4-Reinforced Al2219 Alloy Composites Synthesized by Squeeze Casting Method

Microstructure, Mechanical Behavior, and Tensile Fractography of Si3N4-Reinforced Al2219 Alloy Composites Synthesized by Squeeze Casting Method

Effect of antimony additions on the microstructure and performance of Zn–Mg–Al alloy coatings

Microscopy, electrochemical techniques and mechanical testing are used to investigate the effect of varying antimony additions (0.45–1.8 wt%) on the microstructure and corrosion properties of zinc-magnesium-aluminium coating alloys. Samples were produced by splat casting to produce high cooling rates similar to those seen in a continuous galvanising line. X-Ray Microscopy reveals that the Sb additions produce disk-shaped Mg3Sb2 intermetallics, subsequently reducing or eliminating the MgZn2 eutectic. Electrochemical testing in 1 wt% NaCl shows that the Mg3Sb2 phase is cathodic with respect to the bulk alloy with slower oxygen reduction kinetics. The decrease in eutectic content leads to less intense anodic activity. The combined effect is anodic and cathodic deactivation, which leads to a 43% reduction in corrosion rate as measured through LPR compared to the base alloy. This work shows that quaternary additions to ZMA coating alloys can be a potential route to improved corrosion resistance for galvanic protection.

Friction and corrosion characteristics of microarc oxidation/laser cladding palygorskite coating on 6061 aluminum alloy substrates

In this study, micro arc oxidation (MAO) technology was used to surface coating of 6061 aluminum (Al) disk. Then laser is used to clad palygorskite (Pal) on the surface of the MAO coating to improve the protection of the coating against the Al substrate. The laser irradiates heat onto the Pal powder, the Pal is heated and at the same time the MAO coating is affected by the heat, and the MAO coating is cooled and cured along with the Pal to form the MAO- Pal composite coating. The surface morphology, elemental composition and phase composition of the MAO-Pal coating were analyzed using scanning electron microscopy, energy spectroscopy and X-ray diffraction. And friction experiments were performed on the MAO- Pal coating. The results showed that the coefficient of friction (COF) of the MAO-Pal coating was reduced by 27 % compared to the Al substrate and 19 % compared to the MAO coating under water lubrication conditions. Through the corrosion resistance experiments, the corrosion potential (Ecorr) of the MAO- Pal coating increased by 0.197 V compared to the Al substrate and 0.280 V compared to the MAO coating, and the corrosion current density (Icorr) simultaneously decreased by three orders of magnitude compared to the Al substrate and one order of magnitude compared to the MAO coating. The MAO- Pal coating prepared by laser cladding Pal had good wear and corrosion resistance, which improved the service life and application range of Al alloy and was expected to promote the development of Al alloy in the application field.

In situ conductometry for studying the homogenization of Al-Mg-Si alloys and predicting extrudate grain structure through machine learning

In industrial practice, no sensors capable of obtaining microstructural information in situ during thermo-mechanical processing of Al alloys are commonly employed. Inductive electrical conductivity measurement is safe, inexpensive, and capable of acquiring valuable information about precipitation and dissolution processes. However, commercial eddy current sensors work only at low temperatures near room temperature and are thus not suitable for in situ conductometry during heat treatments of Al alloys. We designed a high-temperature eddy current sensor and performed in situ conductometry during the homogenization of six Al-Mg-Si wrought alloys, three of which are experimental recycling-friendly alloys with increased Fe content. The results are interpreted with regard to microstructural investigations, and the advantages and limitations of our approach are discussed. As a proof-of-concept, we show how the conductivity curves and extrusion process parameters can be combined to predict final extrudate grain structures using machine learning. To achieve this, we employed finite element simulation of extrusion coupled with microstructural simulation over a wide parameter range, validated by extrusion experiments and metallography, and trained a feedforward neural network. We believe our interdisciplinary approach can lead to improvements in the industrial processing of Al wrought alloys.

Evaluation of the effect of strontium and tungsten carbide on the microstructure evolution, tribological and mechanical behaviour of Al-Zn-Mg-Cu-5Sr-WC metal matrix composite

The present study focused on the experimental investigation of the metallurgical, tribological, and mechanical behavior of the developed Al-Zn-Mg-Cu-Sr-WC (Al7075-Sr-WC) metal matrix composite. The effect of the reinforcements such as strontium and tungsten carbide (WC) along with a 2 wt% magnesium as the wetting agent during the stir casting of the synthesized aluminum metal matrix composite (MMC) was investigated by varying the weight percentages. The microstructure examination was characterized using field emission scanning electron microscopy (FE-SEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS) techniques. Wear analysis and mechanical testing were conducted to study the effect of WC particles in the matrix phase by examining their wear rate, tensile strength, proof strength, and hardness values. From the mechanical and tribological tests, it was observed that there was an increase of 55% in hardness and 43% in tensile strength, along with a 31% reduction in wear rate. The secondary phases revealed from XRD analysis lead to more hardness along the refined grain boundaries. The tensile strength of the composite initially increased with a 3 wt% of WC and 5 wt% strontium due to hindrance to the dislocation movement but decreased with more reinforcement particles caused by brittleness. The hard WC particles presence has reduced the wear rate significantly due to its resistance towards abrasive wear and lubricating effect. The unique combination of a grain refiner and a binder helped develop a novel composite with superior characteristics that could replace many aerospace components made up of Al7075 alloy.

Dislocation loop and irradiation-induced synergistic-competitive mechanism in Cu-rich precipitates: a phase-field study

Both irradiation and dislocations have been proposed as routes to rationally manipulate spatial distribution and micromorphology of precipitate. An interesting effect emerges in Fe–10at.%Cu–3at.%Mn–1.5at.%Ni–1.5at.%Al alloy due to the synergistic-competitive roles of dislocation loop and irradiation. Base on cascade mixing, vacancy-interstitial atoms and dislocation stress field model, we examine nucleation and growth dynamics of Cu-rich precipitates, where both dislocation loop and irradiation act in conjunction. Analytical treatments identify regimes, where the distribution of elements and point defects due to irradiation and dislocations are specific to the Cu-rich precipitates. Simulation results reveal that density, size and distribution of Cu-rich precipitates are a manifestation of the competing effects of the dislocation loop and the irradiation rate. More specifically, the dislocation loop preferentially assists the formation of precipitates and new dislocations at lower irradiation rates. Only the irradiation induces the formation of Cu-rich precipitates with the irradiation rate continues to increase. Equipped with molecular dynamics, where reproduces major interaction features of the solutes with point defects under displacement cascade, can verify multi-component morphologies of Cu-rich precipitates. This modeling framework provides an avenue to explore the role of dislocation loop and irradiation on the microstructural evolution of Cu-rich precipitates.

Influence of Graphene/h-BN and SiC/h-BN reinforcing particles on microstructural, mechanical and tribological characteristics of Al7075-based hybrid nanocomposites

Aluminium (Al) based Metal Matrix Composites (MMCs) replaced conventional alloys in numerous sectors like the automotive to aerospace industries. In this investigation, Al7075/Silicon carbide (1 wt%)/Hexagonal-boron nitride (0.5 wt%) and Al7075/Graphene (1 wt%)/Hexagonal-boron nitride (0.5 wt%) hybrid metal matrix nanocomposites (HMMNCs) prepared using an ultrasonic-assisted melt-stirring squeeze casting process. To attain the homogenous mixing of hard ceramic/nanoparticles, reduce the aggregation effect and improve wettability of the reinforcing nanoparticles in the molten slurry. Reinforcement particles mixture (Silicon carbide (1 wt%)/Hexagonal-boron nitride (0.5 wt%) and Graphene (1 wt%)/Hexagonal-boron nitride (0.5 wt%)) have been ball-milled for the duration of 1 to 6 h (hrs). To analyze the morphology of the 1–6 h ball-milled hybrid reinforcing particles mixture was analyzed via scanning electron microscope (SEM). Moreover, microstructural investigation of the Al-based HMMNCs was performed using optical microscopy (OM), field-emission scanning electron microscopy (FE-SEM) and scanning electron microscope (SEM). Also, the dispersal of hybrid reinforcing particles mixture in Al7075-based HMMNCs was examined via SEM-equipped with x-ray mapping analysis. The fabricated Al7075-based HMMNCs are tested for their tensile strength, microhardness and tribological behavior by employing universal testing machines, Vickers microhardness tester and ball-on-disc instruments. Tribological characteristics of the Al7075-based HMMNCs were observed via ball-on-disc tribometer apparatus with load (10, 15 and 20 N), time (15 min) and speed (300, 600 and 900 rpm). While investigating, it is perceived that that the wear, tensile strength, hardness and microstructure characteristics of the Al7075/Silicon carbide/Hexagonal-boron nitride and Al7075/Graphene/Hexagonal-boron nitride HMMNCs were superior over the Al7075 alloy. It is found that Vickers and Rockwell hardness of the Al7075/SiC/h-BN HMMNCs were superior by 36.87% and 16.29%, respectively, over the Al7075 specimen. Whereas, UTS of the Al7075/Graphene/h-BN HMMNCs were superior by 38.19% over the Al7075 alloy.

Enhancement mechanism of low alloying (Mn, Al) and plastic deformation for hydrogen storage kinetics of Mg alloy

The sluggish kinetics are a momentous hurdle for the application of Mg-based hydrogen storage alloys. To improve the kinetics, Mg-xMn-0.5Al alloys (x = 0, 0.5, 1, 2) were fabricated by combining low alloying strategy and plastic deformation. The results demonstrate that both low alloying and plastic deformation enhance the kinetic properties of hydrogen adsorption and desorption. The resulting Mg-2Mn-0.5Al alloy after plastic deformation can absorb ca. 5 wt% hydrogen within 3 min at 623 K, and the dehydrogenation activation energy (ca. 125 kJ/mol) is substantially reduced versus Mg (ca. 166 kJ/mol). The co-addition of Mn and Al can introduce more second phases, and the pinning effect of Al8Mn5 and α-Mn on grain boundaries can promote grain refinement and dislocation proliferation. The increase of grain boundaries, phase interfaces and dislocations accelerates the H atoms diffusion, benefitting the hydrogen absorption. Plastic deformation generates plenty of nanoscaled Al8Mn5 particles, which can serve as additional heterogeneous nucleation sites of Mg during dehydrogenation. Low alloying of Mn and Al combined with plastic deformation is a low-cost and effective way to improve the hydrogen storage kinetics of Mg-based alloys.

A new high-pressure die casting Mg−Gd−Sm−Al alloy with high strength-ductility synergy

A high-pressure die casting (HPDC) Mg−5Gd−1.5Sm−0.7Al alloy was newly developed and exhibits outstanding strength-ductility synergy, with the yield strength and the tensile elongation to fracture being approximately 200 MPa and 8.5%, respectively. This alloy has two types of α-Mg grains: coarse α1-Mg ((46 ± 18) μm) and fine α2-Mg ((9.2 ± 2.3) μm) grains, and various Al-GS (GS = Gd and Sm) particles located at grain boundaries while clear solute-atom segregation near grain boundaries with limited or free intermetallic particles. Characterizations using Cs-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) indicate the crystal structures of Al-GS phases. After aging, dense β′ precipitates and chain-shaped β’’-like structures precipitated near grain boundaries while a high density of ultrafine β’’-(Mg,Al)3Sm precipitates and Al-GS clusters formed in grain center. Relatively fine grains, Al-GS primary particles, solute-atom segregation near grain boundaries, and/or multiple precipitates contribute to the high strength of the studied alloy, while the multi-scale α-Mg grains, variety of intermetallic particles but discontinuous skeleton, and the multi-typed precipitated lead to its satisfactory ductility.

Enhancement of coercivity and thermal stability for Nd-Fe-B sintered magnets by diffusing Dy-Co-M (M=Cu, Al) alloys

Commercial N52 sintered NdFeB magnets were processed by grain boundary diffusion (GBD) with Dy-Co-M (M=Cu, Al) alloys. The coercivity of magnets greatly increase to 17.62 and 18.83 kOe respectively when diffusing Dy58Co25Cu17 and Dy58Co25Al17 alloys, which are obviously higher than that of Dy58Co42 GBD-treated magnet with 16.64 kOe. Further thermal stability studies indicate that the thermal stability of Dy58Co25Cu17 and Dy58Co25Al17 GBD-treated magnets is further improved compared to the Dy58Co42 GBD-treated magnet. The results show that the temperature coefficients of remanence (20–120 °C) are reduced from –0.148%/°C to –0.134%/°C and –0.132%/°C by Dy58Co25Cu17 and Dy58Co25Al17 GBD-treatment, respectively. Besides, the irreversible magnetic flux losses (120 °C) for Dy58Co25Cu17 and Dy58Co25Al17 diffusion magnets are 4.76% and 2.79%, respectively. Microstructural analyses demonstrate that the presence of Cu and Al elements reduces the excessive accumulation of Dy and Co on the surface in the diffusion magnets and improves the diffusion depth and utilization of Dy and Co. Furthermore, the flow of Co from the triple junction phase to the thin grain boundary phase is promoted, which contributes to the uniform distribution of Co. In addition, the dynamic evolution of the magnetic domain structure during the temperature rise process was studied. This work provides insight into the preparation of high-performance and high-thermal stability magnets.

Effects of Ag/Sc microadditions on the precipitation of over-aged Al–Zn–Mg–Cu alloys

Microalloying addition plays a significant role in controlling the characteristics of precipitates in Al alloys. This study investigates the effects of Ag and Sc microalloying addition on the thermal stability of Al–Zn–Mg–Cu alloys, via differential scanning calorimetry, transmission electron microscopy, and atom-probe tomography. The results demonstrate that Ag and Sc additions increase the number density of η-MgZn2 type nano-precipitates (formed during heat treatment) by forming direct (Mg–Ag phase, prototype of precipitate) or indirect precursors (Al2Sc phase, constituent of precipitate) for the precipitate. In addition, the Ag and Sc elements can effectively prevent the coarsening of η precipitates and facilitate the high-density distribution of fine η precipitates, during the over-aging period, improving the thermal stability of the Al–Zn–Mg–Cu alloys. The thermal stability is particularly improved by Ag addition because Ag atoms directly prevent the coarsening of η precipitates by hindering Zn diffusion into the precipitate. On the contrary, Sc addition indirectly prevents the coarsening of η precipitates by depleting the solute species from the Al matrix, enabling abundant precipitates limited growth. Thus Ag addition improves precipitation strengthening by preventing the coarsening of precipitates during over-aging.

Exploring Elemental Powder Approach for Making Al and Ti Containing High-Entropy Alloys by Powder Bed Fusion

This research aimed to produce high-entropy alloys (HEA), namely Mn–Fe–Co–Ni + 5Al and Mn–Fe–Co–Ni + 5Al + 5Ti, through the Powder Bed Fusion technique using elemental powders. Alloy composition has been selected to achieve a HEA matrix with strengthening intermetallic precipitates. Thermo-Calc software has been used to predict solidification behavior and phase stability for non-equilibrium conditions. The experiment involved the execution of an additive manufacturing process with a laser working in point-by-point exposure mode to produce samples using varying laser power and exposure time. The samples underwent investigation via macroscopic examination, porosity analysis, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and hardness testing. Results have shown that processing parameters and alloy constituents directly influenced processability and sample traits. What is more, a high-energy laser beam introduction to the material during the process has helped mitigate the formation of large Ti or Al oxides. In addition, EDS analysis indicated that higher Volumetric Energy Density values enhanced the uniformity of chemical composition, indicating that homogeneity can be achieved by selecting appropriate melting parameters. The results clearly show that these alloys can be successfully (by means of porosity and homogeneity) manufactured from elemental powders via the powder bed fusion technique.

The anodic dissolution kinetics of Mg alloys in water based on ab initio molecular dynamics simulations

AbstractThe corrosion susceptibility of magnesium (Mg) alloys presents a significant challenge for their broad application. Although there have been extensive experimental and theoretical investigations, the corrosion mechanisms of Mg alloys are still unclear, especially the anodic dissolution process. Here, a thorough theoretical investigation based on ab initio molecular dynamics and metadynamics simulations has been conducted to clarify the underlying corrosion mechanism of Mg anode and propose effective strategies for enhancing corrosion resistance. Through comprehensive analyses of interfacial structures and equilibrium potentials for Mg(0001)/H2O interface models with different water thicknesses, the Mg(0001)/72 H2O model is identified to be reasonable with −2.17 V vs. standard hydrogen electrode equilibrium potential. In addition, utilizing metadynamics, the free energy barrier for Mg dissolution is calculated to be 0.835 eV, enabling the theoretical determination of anodic polarization curves for pure Mg that aligns well with experimental data. Based on the Mg(0001)/72 H2O model, we further explore the effects of various alloying elements on anodic corrosion resistance, among which Al and Mn alloying elements are found to enhance corrosion resistance of Mg. This study provides valuable atomic‐scale insights into the corrosion mechanism of magnesium alloys, offering theoretical guidance for developing novel corrosion‐resistant Mg alloys.

Mechanical and wear characteristics of aluminium-7075/graphene/TiB2 prepared by stir casting

The rapid development of Aluminium composites with advanced hybrid materials is increasing due to increasing demand. This composite material is used in many applications in the aerospace and automotive industries due to its lightweight, good corrosion resistance and high thermal resistance. To meet this demand, this study focused on the development of Al-7075 alloy reinforcements containing TiB2 and graphene, using Aluminium-7075 as the base material, mixed with TiB2 and graphene to measure and improve mechanical and tribological properties by using stir casting technique, with the proposed graphene content of 1%, 2% and 3% and TiB2 content varying between 1 to 15% of its overall weight. With the addition of TiB2 and graphene properties such as hardness, tensile strength, impact strength and tribological behaviour are improved. The 12% reinforcement combination (i.e. 10% TiB2 and 2% Gr) exhibit better tensile strength, hardness and wear resistance. Microstructure and phase characterization of the composite material are analyzed using scanning electron microscopy (SEM) and x-ray diffraction (XRD) techniques. A microstructure evaluation is employed to justify the homogenous dispersal and the existence of reinforced particles. To ensure the quality and reliability of products made from these alloys, destructive tests are often conducted to evaluate their mechanical properties and behavior under different loading conditions.

Effect of varying temperature on sintering SiC/B4C reinforced Al6061 alloy composites using vacuum sintering method

The current investigation involved the fabrication of Al6061/SiC/B4C composites with different sintering temperatures using the vacuum casting technique. The morphology and mechanical properties of these composites were then analyzed and are summarized. Morphology studies show that increasing the sintering temperature leads to notable grain refinement, even distribution of reinforcement, and minimal porosity. The incorporation of SiC and boron carbide particles into the matrix enhanced the hardness of 18.37% of the composites by serving as a hindrance to the movement of the matrix lattice dislocations. An increase in sintering temperature results in greater plastic deformation of composites, hence cracks formed and propagated easily due to their brittle nature ultimately reducing the impact strength of composites. The robust adhesion between the Al6061 matrix and the SIC and boron carbide particulates in particle-reinforced composites efficiently inhibited delamination and decreased the rate of wear composites.

Experimental investigation in enhancing the mechanical, wear and corrosion resistance properties of Al6061-SiC-NSA composites fabricated using stir casting process

The study investigates the mechanical, and tribological properties of Al6061-SiC-NSA hybrid composites. The characterization via FE-SEM reveals NSA particle’s crystal structure and agglomeration, with an average particle size of approximately 400 nm. The EDS analysis confirms the presence of oxides (TiO2, SiO2, Fe2O3, Al2O3) along with calcium and potassium. The XRD spectra corroborate these findings, additionally identifying Calcite and intermetallic compounds. The Al6061–5SiC-10NSA composites has improved compressive strength of 254 MPa compared to 220 MPa for base Al6061 alloy. The tensile strength of base Al6061 (100 MPa) decreased to 70 MPa for Al6061–5SiC-20NSA composites. The tensile strength decreases with increasing NSA content. Fracture analysis indicates ductile fracture mechanisms, supported by FE-SEM images displaying honeycomb-like structures and dimples. Impact testing reveals reduced impact strength in composites compared to Al6061 (26J3), with Al6061–10SiC-5NSA exhibiting the best toughness of 22.5 J3. Density decreases in composites, with density of Al6061–5SiC-20NSA composites has reduced to 2.40 g cm−3. The microhardness of Al6061–10SiC-5NSA has better value of 109 HV, whereas further addition of NSA has resulted in decrease in microhardness of composites. Pin-on-disc wear tests demonstrate improved wear resistance with increased NSA content, with Al6061–5SiC-20NSA outperforming other compositions. COF decreases with increased NSA content and sliding speed. FE-SEM analysis of worn surfaces reveals that the major wear mechanism is adhesive wear followed by delamination, further the oxide formation along the surface aiding wear resistance of the composites. Tafel testing indicates decreased corrosion potential with increased NSA content, with Al6061–5SiC-20NSA exhibiting improved corrosion resistance.

First-principles insights into solute partition among various nano-phases in Al−Cu−Li−Mg alloys

First-principles energetics calculations were performed over a group of 25 candidate elements, to investigate their partition energies and behaviors among major nano-phases (δʹ-Al3Li, θʹ-Al2Cu, T1-Al6Cu4Li3 and S-Al2CuMg) in most commercial Al−Cu−Li−Mg alloys. It was revealed that principal alloying element Li cannot directly affect θʹ and S, Cu cannot directly affect δʹ, Mg cannot directly affect θʹ and δʹ but can weakly partition into T1. As for micro-alloying elements, Si is the only element that can partition into all the four nano-phases. Au can partition into δʹ, θʹ and S. Cd can partition into δʹ, T1 and S. Zr can partition into δʹ and T1. Ni substitution can weakly partition into θʹ and S. Ti, V, Zn, Ag and Mo can partition into δʹ only. Cr, Mn, Fe and Co cannot directly affect any of the four nano-phases. Almost all RE-elements can strongly partition into T1, δʹ and S, but would be expelled by θʹ. Only Sc is somehow particular to S, showing no partition preference in S. The newly obtained fundamental results could constitute a simple prototype database in support for the accelerated design of Al−Li based alloys and other related Al alloys.

Analysis of Blackening Reaction of Zn–Mg–Al Alloy Coated Steel Prepared by Anodizing Process

The rising demand for black-treated steel faces challenges with conventional black painting due to issues like scratching and peeling, impacting corrosion resistance and aesthetics. This study explores an alternative method, anodic oxidation, to blacken the surfaces of galvanized or coated steel plates. Parameters like temperature, duration, current density, and gas type were varied during the blackening process. The investigation aimed to identify key factors influencing the blackening. Scanning electron microscopy observed the morphology, while energy-dispersive X-ray spectroscopy and glow discharge mass spectrometry analyzed the chemical composition distribution. X-ray diffraction and X-ray photoelectron spectroscopy conducted compound crystal structure analysis. Results indicate higher temperatures, longer durations, and higher current densities improve blackening through anodic oxidation. Increased magnesium proportion on the surface leads to roughness and porous magnesium oxide formation, enhancing light absorption and explaining the observed blackening effect.

Laser welding of additively manufactured AlSi10Mg and conventionally manufactured Al6061 alloy

Laser welding of additively manufactured AlSi10Mg and conventionally manufactured Al6061 alloy

Comparative analysis of mechanical properties of SiC particle addition on Al6061/Ni and Al6061/Cr metal matrix composites

This research paper investigates the mechanical characteristics of Al6061/Nickel (Ni) and Al6061/Chromium (Cr) metal matrix composites (MMCs) with varying proportions of Ni and Cr by weight. The proportions of Ni and Cr range from 0% to 2.7% weight. Experimental results reveal that the optimum mechanical properties are achieved at 1.8% weight for Ni. Subsequently, SiC (silicon carbide) particles are added to Al6061/Ni MMCs at varying weight percentages (0%, 1%, 3%, 5%, and 7%) to evaluate their impact on performance. The study demonstrates that the combination of 1.8% Ni and 7% SiC in Al6061 exhibits the most favorable properties. Tensile test is carried out with ASTM D 3552 standard; Flexural strength is assessed through ASTM D790, Microhardness by ASTM E384, and Impact strength by ASTM D256. Overall, Al6061/Ni MMCs exhibit superior mechanical performance compared to Al6061/Cr MMCs, with Al6061/Cr MMCs excelling in elongation, flexural strength, and impact strength. This investigation confirms that the addition of nickel and chromium to the Al6061 alloy induces structural modifications that enhance its mechanical properties. The findings provide valuable insights for optimizing the design and fabrication of MMCs for various engineering applications.