Al Alloy Research Articles

Sheet-based friction stir additive manufactured 6061 aluminium alloy: Microstructure, texture evolution and mechanical properties

A 6061 Al alloy build consisting of 3 additive layers was successfully fabricated using a sheet-based friction stir additive manufacturing process. The study focused on analyzing the microstructure and texture characteristics in the central regions of each layer and the thermal mechanical affected zones (TMAZs) beneath the stir zones (SZs). Mechanical properties of the final multilayered build were also analyzed. The results revealed that, following plastic deformations and thermal cycles, the equiaxed grains formed in the central region of layer 2 were the finest (∼7.9 μm) among the three layers, attributed to the highest degree of recrystallization. Additionally, the average grain size of the TMAZs further decreased to ∼4.0 μm due to lower frictional heat generated by the tool pin. Furthermore, the geometrically necessary dislocation densities of the TMAZs showed a slight increase compared to those of the central regions. In terms of textures, shear and deformation textures were predominant in the central regions, while shear texture dominated the TMAZs. The primary precipitates found at the center of the SZs included β, β′, Q′, Al8Fe2Si and (Fe,Mn,Cr)3SiAl12. Besides, the yield strength and ultimate tensile strength of the build drop significantly to 119.7 MPa and 204.6 MPa, respectively. Moreover, a non-monotonic decrease in hardness as the increase of distance from the top of build could be found, due to the existence of numerous grains with soft orientations and the intense dissolution and coarsening of β” and β’ phases.

Weld quality monitoring in friction stir lap joining of dissimilar Al6061 to polycarbonate using thrust–torque-based process stability signatures

The joining of dissimilar aluminium-based alloys to thermoplastic polymers is highly challenging which indicates the necessity of friction welding procedures. The present work addresses the degrees of steadiness in welding thrust-torque to monitor the lap weld contour of aluminium alloy (Al6061) overlapped on polycarbonate sheet or vice versa using friction stir welding. The primary objective was to compare the monitoring capability of the weld non-uniformity by using raw signals and stability signature of welding thrust and stirring torque. Further, these stability indices were used for the prediction of weld mechanical behaviour using response surface methodology. The stability signatures were found to be a better indicator of weld profile unevenness than raw signals as it was an amplified version of the local deviations in welding thrust-torque. Improved strength efficiency up to 49% was noticed in PC-Al welds due to improved process stability at intermediate tool traverse (55 mm/min) and revolving speeds (1100 rpm). The stability in stirring torque was better indicator of weld quality features than tool thrust steadiness in Al-PC lap while it was reversed in PC-Al lap. Thus, the thrust force instability was mostly indicated the joint ductility while combined steadiness in thrust-torque were essential for the prediction of weld strength. The higher stability index in tool thrust (≥7.5) with ample torque steadiness (5–8) can upgrade the Al-PC weld strength (≥20 MPa), whereas intermediate thrust stability (6–6.5) with high stable torque (≥7) can uplift the joint strength (≥25 MPa) in PC-Al welds.

Stability and properties of six new Ru3Al structures: A first-principles study of mechanical, electronic, and superconducting properties

Ruthenium–aluminium (Ru–Al) alloys demonstrate excellent properties; however, the Ru3Al structure has a higher formation energy than those of other Ru–Al structures. Herein, to identify more stable Ru3Al structures, we employed the CALYPSO code and discovered six stable structures: one hexagonal structure, two monoclinic structures and three orthorhombic structures. First-principles calculations and the density functional theory were used to assess their mechanical, electrical and superconducting properties. The formation energies of these newly discovered Ru3Al structures were lower than those of previously proposed structures, confirming their thermodynamic stability. Elastic constant calculations indicated that all the structures were mechanically stable and ductile. Moreover, electronic structure analyses revealed that the structures were metallic, primarily owing to the contribution of Ru d orbitals. Phonon dispersion and density of states analyses also confirmed the dynamic stability of the structures, with low-frequency phonons contributing considerably to electron–phonon coupling. The superconducting transition temperatures (Tc) of the structures were calculated using the Allen–Dynes-modified McMillan equation. The Cmcm structure showed the highest Tc of 3.99 K, and the P2/c structure showed the lowest Tc of 1.56 K. Overall, this study identified six novel and stable Ru3Al structures with good mechanical and superconducting properties, potentially advancing the development of Ru–Al-based superconductors.

Influence of martensite and grain size on the mechanical behavior of austenitic Fe–C–Mn–Ni–Al medium Mn steels with TWIP mechanism under uniaxial tension/compression and micromechanical creep

Medium Mn steels with induced plasticity mechanisms have effectively addressed the high-strength and ductility requirements for structural applications. However, there is still uncertainty about the impact of residual martensite on medium Mn steels with an austenitic matrix under uniaxial tension and compression. Furthermore, research on the influence of grain size through incomplete recrystallization in medium Mn alloys is scarce. In this context, our study focused on design and manufacturing a medium Mn Fe–C–Mn–Ni–Al alloy through controlled atmosphere casting incorporating martensite, aiming to analyze its effects under uniaxial stress conditions. Thermomechanical and annealing heat treatments were applied to control grain growth and nucleation of new grains, allowing us to explore how grain size affects the twinning process and mechanical reinforcement in the alloy. Microstructural characterization techniques, including optical and scanning electron microscopy, were employed to assess the mechanical response and damage mechanisms. Mechanical tests included tension, compression, and nanoindentation. The results indicated that residual martensite generates an accelerated damage mechanism under tension due to co-deformation at the interface with austenite, resulting in crack nucleation and rapid propagation through mode I fracture. Consequently, ductility in tension significantly decreases, while no apparent failure is observed during the compression deformation process. Furthermore, incomplete recrystallization was observed to enhance the creep response in both tension and compression. The strain hardening rate results revealed the activation of primary twinning in tension and both primary and secondary twinning in compression for annealed samples. Nanoindentation tests confirmed the presence of twinning and revealed that diffusion creep and grain boundary sliding are the predominant creep mechanisms.

Orthogonal cutting of 3D printed multi-material workpiece: numerical investigation of machining forces, stress, and temperature distribution

AbstractWith the development of 3D metal printers for rapid prototyping and industrial component production, heightened attention was directed towards post-processing operations for achieving precise surface quality and geometrical tolerances for these components. This paper investigated the orthogonal cutting of multi-material 3D printed workpieces using a coated cutting tool through finite element simulation. The workpieces featured different horizontal and vertical arrangements of layers composed of aluminum 7075-T6 alloy (Al), stainless steel 316 low alloy (SS), and Ti6Al4V alloy (Ti). The study explored the impacts of multi-material composition, coating thickness, and the rake angle of the cutting tool on machining forces, stress distribution, temperature distribution, and chip formation geometry. The results revealed a bimodal chip morphology in the machining process of horizontally arranged SS layers combined with other alloys. The SS layer resulted in a relatively uniform chip formation, while layers with two other materials exhibited a serrated chip formation. In contrast, a discontinuous chip formed when combining Al and Ti materials, as well as in the horizontally arranged layers made of Al, SS, and Ti alloys. The cutting force increased by 2.26 times when cutting workpieces with the horizontal arrangement of SS and Al layers compared to those with a single Al material. For the horizontal and vertical arrangement of layers made of Al and SS, von Mises stress values over the edge of the coated cutting tool significantly increased where the tool contacted the SS layer. Additionally, the horizontal arrangement of layers made of Al and SS materials caused the coated cutting tool to exhibit an extensive temperature distribution, with the maximum recorded temperature reaching 1448 °K. Increasing coating thickness led to a decrease in maximum principal stress at the surface of the tool and a rise in temperature at the cutting edge of the insert.

Influence of surface state on interface bonding strength of Al/Ta laminated composite via differential temperature rolling

Al/Ta laminated composite is one of the promising space radiation shielding materials. However, due to significant differences in the properties of Al and Ta alloys, the interface bonding strength of rolled Al/Ta laminated composites is weak. In this study, we prepared 2A12 Al/Ta-2.5W laminated composite using differential temperature rolling method. The influence of surface state on the interface microstructure and interface bonding strength were systematically analyzed, and the interface bonding mechanism of Al/Ta laminated composite was revealed. It is found that 2A12 Al and Ta-2.5W alloys are successfully bonded via differential temperature rolling within rolling temperature range of 350∼450 °C and rolling reduction range of 40 %–50 % when the hardening degree of Ta-2.5W surface layer exceeds 25 %, and the roughness of Ta-2.5W and 2A12 Al surface is greater than 4.5 μm and 3.6 μm, respectively. It is demonstrated that increasing the hardening degree and roughness at Ta-2.5W surface, while decreasing the hardening degree and increasing roughness at 2A12 Al surface can facilitate cracking of the surface layer at Ta-2.5W side and the embedding of virgin Al metal into the cracks during rolling, which can promote the interface bonding process between 2A12 Al and Ta-2.5W alloys. The highest interfacial bonding strength of Al/Ta laminated composite can reach 41.2 MPa. However, when the surface layer at Ta-2.5W side is excessively hardened and the hardness reaches two times of the substrate, thick fragments could be generated at the interface, which have detrimental effect on the interface bonding strength and the value decreases to 23.05 MPa. In terms of the effects of rolling temperature and rolling reduction, it is found that the oxide film and hardening layer on the Ta-2.5W surface are more sufficiently ruptured, and more virgin 2A12 Al metals are embedded in the cracks at the surface of Ta-2.5W at higher rolling temperature and higher rolling reduction conditions, thereby leading to the increased interface bonding strength. This study provides theoretical basis for the preparation of Al/Ta laminated composites and sheds light on the relationship between surface state and interface bonding strength of laminated metal composites.

Durable one-component polyurea icephobic coatings with energy-saving performance in electrical heating de-icing

Ice formation and accumulation on the surfaces of aircraft, wind turbines, and boat hulls might result in serious economic losses and catastrophic accidents. The development of a new generation of icephobic surfaces has emerged in recent years for anti-icing. However, insufficient durability of the existing icephobic surfaces remains a significant challenge to their applications. In this study, durable one-component polyurea icephobic coatings (OPICs) with a low ice adhesion strength (∼25.3 kPa) were prepared via a solvent-free method by combining the NCO-terminated prepolymer, latent curing agent, and silicone oil. The chemical structure, surface morphology, wettability, mechanical properties, icephobicity, and durability of the OPICs were studied. The optimized design of OPICs with synergistic icephobic mechanisms endowed them with excellent icephobicity and durability. The superior mechanical durability and chemical stability were revealed by the maintaining icephobicity of OPICs even after 3000 continuous Taber abrasion cycles, as well as 50 icing/de-icing cycles, 72 h of NaOH immersion, and 240 h of neutral salt spray test. The effect of OPICs on minimizing the electric power consumption was further investigated by icing wind tunnel. In comparison to the epoxy primer coated and Al alloy coated airfoil surface, airfoil surface coated by OPIC-30 was found to achieve about 43.7 % and 43.9 % energy savings in the keeping entire airfoil surface ice-free, respectively. The one-component polyurea icephobic coatings have great prospects for practical applications that require long-term anti-icing properties.

Effect of Nonessential Alloying Elements and Solution pH on Corrosion Behavior of Al-Mg Alloys Fabricated by Cold Spray Deposition

This paper highlights the difference in corrosion behavior of cold spray (CS) deposited AA5083 and Al-5.0 wt% Mg alloys with an emphasis on the effect of nonessential alloying elements and solution pH. CS process is an emerging technology for repairing damaged structures via solid-state deposition. While recent works have focused on CS Al alloys, less attention has been paid to CS Al binary alloys in comparison to Al engineering alloys, which have important implications for the integrity of structural components repaired by the CS process. Herein, the microstructure of CS AA5083 and Al-5.0 wt% Mg binary alloy was analyzed using various microstructure characterization techniques. Corrosion behavior was assessed using electrochemical and immersion tests in 0.6 M NaCl (pH 8.3 and 11.5) solution. Intermetallic phases, such as Fe- and Si-containing phases, in CS AA5083 decreased corrosion resistance by increasing cathodic kinetics in a near-neutral solution. In addition, immersion tests demonstrated lower corrosion resistance in CS AA5083 than in CS Al-5.0 wt% Mg, whereas an alkaline environment showed the presence of a secondary passive layer on CS AA5083, providing higher corrosion resistance compared to CS Al-5.0 wt% Mg.

Study of Intergranular Corrosion Behaviors of Mn-Increased 5083 Al Alloy with Controlled Precipitation States of Al6Mn Formed during Homogenization Annealing

In this study, as a vital part of the production of Mn-increased 5083 Al alloy, i.e., homogenization annealing before hot rolling, the target states of key Al6Mn precipitation, including the dispersed, initial coarsening and intensive coarsening states, were designed, and the corresponding precipitates formed via the control of the temperature and holding time in the annealing process. By means of metallographic corrosion and nitric acid mass loss tests (NAMLT) for assessing the intergranular corrosion (IGC) resistance, temperatures ranging from 175 °C to 225 °C were determined to induce a transition from sensitization to stabilization for this innovative 5083. At a temperature of 175 °C for a duration of up to 24 h (2 h, 4 h, 8 h, 16 h, 24 h), the results show that when the soak time is 24 h, the sample with initially coarsened Al6Mn phases has a lower degree of sensitization (DOS) compared to the samples with Al6Mn phases in both the dispersed and intensive coarsening states, and its NAMLT is reduced by 11% and 15%, respectively. Subsequently, transmission electron microscopy (TEM) analysis has investigated that for the sample with the best IGC resistance, i.e., that with initially coarsened Al6Mn phases, plate-like Al6Mn particles (200~500 nm) can act as heterogenous nucleation sites for β phases, driving their preferential precipitation on Al6Mn particles and resisting their precipitation along grain boundaries, ultimately improving the IGC resistance of 5083 Al alloy after homogenization annealing.

Enhancing tensile and fatigue properties of high-speed-extruded Mg–5Bi–3Al alloy using non-homogenized extrusion billet

This study aims to improve the tensile and high-cycle fatigue properties of a high-speed-extruded BA53 (Mg–5Bi–3Al, wt.%) alloy using a non-homogenized extrusion billet. Homogenization treatment of the BA53 billet leads to a significant reduction in the area fraction of Mg3Bi2 particles from 12.9% to 2.5% and an increase in the average grain size from 142 to 189 μm. The BA53 material produced via the high-speed extrusion of the cast billet (Cast-E) and that produced via the high-speed extrusion of the homogenized billet (Homo-E) both exhibit a fully recrystallized microstructure. However, Cast-E has a finer grain size and many more Mg3Bi2 particles than Homo-E. In addition, the tensile yield strength and elongation of Cast-E are 211 MPa and 9.4%, respectively, higher than those of Homo-E (198 MPa and 7.9%). This higher strength is attributed to the strengthening effects of the higher number of Mg3Bi2 particles, the finer grain size, and the higher internal strain energy. The fatigue limit for Cast-E is 100 MPa, which is 25% higher than that of Homo-E (80 MPa). This occurs because the numerous fine Mg3Bi2 particles in Cast-E inhibit the formation of persistent slip bands on the specimen surface and impede crack propagation. This study proposes a new manufacturing process that does not require billet homogenization, thus simultaneously improving the productivity of the extrusion process and the tensile and fatigue properties of the resulting BA53 alloy.

Influence of sub-zero coolant circulation and additive nanoparticles on performance characteristics of FSPed Al6061 alloy

ABSTRACT Al6061 alloy has become prevalent in the industrial sector because of its low density, excellent machinability, and corrosion resistance but it lacks properties like hardness and wear. Therefore, surface modifications by friction stir processing (FSP) are done with additive nanosized particles like multi-walled carbon nanotubes (MWCNT), Titanium oxide (TiO2), and Graphene nanoparticles (GNP) To perform 2-pass FSP, a uniquely engineered fixture with coolant circulated underneath the plate at sub-zero temperatures is used. Grain refinement has been observed in micrographs as a consequence of 2-pass FSP. The coolant circulated beneath carries the heat generated and enhances the heat dispersion rate, culminating in finer grains. The calculated mean grain size of the Al6061 alloy was considerably decreased in all the surface composites. There is a substantial improvement in the microhardness profile, which has increased by nearly 70–90%, as well as a significant enhancement in tensile strength of almost 20–30% in all the composites. The ductile type of failure during tensile load is revealed by SEM fractography. The process of dynamic recrystallisation is responsible for the development of equiaxed grains. The wear resistance of all the composites is also enhanced, and the COF of Al6061/GNP composite is found to be lowest at 0.23.

Annealing Behavior of a Mg-Y-Zn-Al Alloy Processed by Rapidly Solidified Ribbon Consolidation.

Mg-Y-Zn-Al alloys processed by the rapidly solidified ribbon consolidation (RSRC) technique are candidate materials for structural applications due to their improved mechanical performance. Their outstanding mechanical strength is attributed to solute-enriched stacking faults (SESFs), which can form cluster-arranged layers (CALs) and cluster-arranged nanoplates (CANaPs) or complete the long-period stacking ordered (LPSO) phase. The thermal stability of these solute arrangements strongly influences mechanical performance at elevated temperatures. In this study, an RSRC-processed Mg-0.9%, Zn-2.05%, Y-0.15% Al (at%) alloy was heated at a rate of 0.666 K/s up to 833 K, a temperature very close to melting point. During annealing, in situ X-ray diffraction (XRD) measurements were performed using synchrotron radiation in order to monitor changes in the structure. These in situ XRD experiments were completed with ex situ electron microscopy investigations before and after annealing. At 753 K and above, the ratio of the matrix lattice constants, c/a, decreased considerably, which was restored during cooling. This decrease in c/a could be attributed to partial melting in the volumes with high solute contents, causing a change in the chemical composition of the remaining solid material. In addition, the XRD intensity of the secondary phase increased at the beginning of cooling and then remained unchanged, which was attributed to a long-range ordering of the solute-enriched phase. Both the matrix grains and the solute-enriched particles were coarsened during the heat treatment, as revealed by electron microscopy.

Droplet transition behavior and compositional homogenization of TiAl alloys fabricated via dual-wire electron beam-directed energy deposition

The dual-wire electron beam-directed energy deposition (EB-DED) process presents considerable advantages for fabricating titanium aluminide (TiAl) alloys via in situ reactions between Ti and Al. However, variations in the thermophysical properties of pure Ti, pure Al, and TiAl alloys pose challenges in achieving consistent droplet transition behavior and uniform chemical composition. This study explored the effects of wire feeding modes on the forming quality of TiAl alloys and droplet transition behaviors and discussed compositional homogenization and elemental evaporation in TiAl alloy components. Both single-side and double-side feeding modes were utilized, and the electron beam directly melted the Ti wire in the double-side mode, thereby achieving superior surface morphology. Random disturbances and suboptimal wire feeding angles led to the wires deviating from the electron beam center and then being inserted into or passing through the molten pool, thereby degrading the forming quality. By positioning the Al wire tip beneath the Ti wire tip, a common droplet emerged as the Ti droplets melted the Al wire. The droplet transition behavior was regulated by the distance between the wire tips and component surfaces, achieving a liquid bridge transition at distances ranging from 0.75 to 5.82 mm. Although the droplet composition was generally uniform owing to elemental evaporation, the fluctuations among the droplets exceeded those observed in the as-deposited components. The extensive molten pool and keyhole effect enhanced compositional homogenization within the TiAl alloy components. During the deposition process, the evaporation rate of Al surpassed that of Ti due to its higher saturation vapor pressure, consequently yielding a lower actual Al content. The loss rate of Al initially decreased and then increased as the calculated Al content increased, which was influenced by the Al content in the molten pool and temperature variations. This research advances the fundamental understanding of TiAl alloy fabrication via in situ reactions and contributes to the development of the EB-DED process.

Corrosion and mechanical properties of Al/Al2O3 composites fabricated via accumulative roll bonding process: Experimental and numerical simulation

With the advancement of science and technology and the construction of metal-based composites (MMC), it became possible to achieve improved properties that were not easily available in an alloy. In fact, with the emergence of such technology, manufacturers were able to adjust the resulting materials according to their needs in such a way as to provide mechanical strength, hardness, corrosion resistance, or other desired properties. These composites were used in various aerospace, automotive, construction, and production industries. Aluminum-based composites are among the structures that have taken an important place in the industry due to their lightweight and high strength. The present study produced bi-alloy aluminum-based 1060/5083 composites fabricated with alumina particles with a Hot ARBp at T = 380 °C. Also, the effect of rolling steps on the roll bonding mechanism is investigated using numerical simulation. As the novelty of this study and for the first time, a bi-alloy 1050/5083 composites reinforced Al2O3 particles via ARB process have been produced and then, potential dynamic polarization in 3.5 Wt% NaCl solution was used to study the corrosion properties of these composites. The corrosion behavior of these samples was compared and studied with that of the annealed aluminum. The study aimed to investigate the bonding behavior between the bi-alloy layers. So, as a result of enhancing influence on the number of ARBp, this experimental investigation revealed a significant enhancement in the main electrochemical parameters and the inert character of the Alumina particles. Reducing the active zones of the material surfaces could delay the corrosion process. Results showed that the corrosion resistance of the sample fabricated after six steps improved more than 100 % in comparison with the initial annealed Al alloy. Also, the average peeling force improved from 45 N to 94 N for the sample fabricated with six steps. Moreover, at a higher number of steps, the corrosion of MMC improved. Moreover, increasing the number of ARBsteps illustrated an improvement in the wear resistance of samples. Finally, the samples' bonding interface, corrosion surface, and peeled surface were investigated using scanning electron microscopy (SEM).

Ultrasonic-induced amorphization and strengthening mechanisms of ultrasonic vibrations assisted friction stir Al/Ti welds

Integration of aluminum (Al) and titanium (Ti) alloys offers an effective approach to sustainable and high-quality development of the automotive and aviation industries. However, challenges arise when welding Al alloys to Ti alloys due to the formation of detrimental intermetallic compounds at the interface. With the implementation of ultrasonic vibrations, the temperature and strain rate were both increased during Al/Ti friction stir welding (FSW), leading to the formation of an amorphous interlayer, instead of intermetallic compound (IMC), at the interface. The interfacial microcracks were eliminated in the ultrasonic vibrations assisted friction stir welding (UVFSW). There were Ti particles separated from the Ti substrate and dispersed in the Al alloy, thereby resulting in a more gradual and moderate evolution of the interfacial microstructure. Due to the improved interfacial microstructure with ultrasonic vibrations, the lap shear strength was almost twice that of the conventional FSW welds within same welding conditions. Meanwhile, ultrasonic vibrations also improved the fabrication efficiency with a higher optimal traversing speed. The failure mode shifted from interface separation of FSW welds to a shear dimple fracture of the UVFSW welds, demonstrating the better plasticity and reliability of the UVFSW Al/Ti dissimilar joints.

Secondary phase increases the elastic modulus of a cast aluminum-cerium alloy

Alloying in metal castings is one of the principal methods of strengthening an alloy for various structural and functional applications, but very rarely does it modify an alloy’s elastic modulus. We report a methodology of combining isostructural Laves phases to form a multi-component, high symmetry, isotropic phase that was discovered to enhance the elastic modulus of a cast aluminum alloy to 91.5 ± 7.4 GPa. Flux grown single crystals of the rhombicuboctahedron phase (RCO), so named for the observed morphology, were used to enhance understanding of the structure and mechanical properties of the phase. The pure RCO phase’s structure and site occupancies were co-refined using x-ray and neutron diffraction. Dynamic nanomechanical testing of the cast alloy shows the primary RCO phase has a high, relatively isotropic, elastic modulus. This RCO containing aluminum alloy is found to have a specific modulus that exceeds that of the leading Al, Mg, Steel, and Ti alloys.

Investigation on Be, Mg, Ca, B, Ga, C, Si, and Ge atoms doped on Al (111) surface and their effect on oxygen adsorption: A first-principle calculation

Oxygen corrosion of the aluminum alloy has a substantial impact on the durability of engineering materials and equipment. To better understand how various alloy elements affect oxygen corrosion, we used first-principle DFT method to study the role of each given dopant atom (Be, Mg, Ca, B, Ga, C, Si, and Ge) in the formation of surface oxide film on the Al (111) surface, in the case replacing a surface Al atom. Our calculations show that the electron gain or loss abilities of these alloy elements differ from that of Al metal, with Be, B, C, and Si atoms tending to penetrate into the surface, Mg, Ca, and Ga atoms protruding, and Ge atom just embedded into the Al (111) surfaces. Additionally, the type of doping element at the Al (111) surface can greatly affect the O2 absorption, predicting that Ca-doped surface absorb the least amount of oxygen, followed by Si-doped surface, with Be-, Mg-, B-, Ga-, C-, and Ge-doped surfaces showing higher O2 absorption. Based on adsorption energy (Eads) and partial density of states (PDOS) analysis, we conclude that the doped Al (111) surfaces can make O2 adsorption different owing to the difference in electronic properties of the doping atoms. These insights draw a greater knowledge of the role of alloy elements in the oxygen corrosion of Al alloys, enabling guidance for designing more corrosion-resistant materials.

Effect of thickness ratio on microstructure evolution and coordinated behavior of Mg/Al composite plates in one-pass asymmetric rolling with differential temperature rolls

To explore how varying matrix thicknesses influence interfacial morphology, microstructure, and mechanical properties of Mg/Al composite plates, this study prepared composite plates with distinct thickness ratios using an asymmetric rolling process featuring differential temperature rolls. The findings indicate that the Mg alloy largely exhibits significant recrystallization and sub-grained, while the Al alloy largely demonstrates a sub-grained characteristic. Notably, there exists a strong positive correlation between bonding strength at the interface and thickness ratio. As the thickness ratio increases, enhanced shear deformation at the interface triggers more slip system initiation, resulting in a gradual reduction of texture intensity in both the Mg and Al layers. Specifically, when the AZ31B/Al6061 thickness ratio reaches 5, the recrystallization level of the Mg layer is relatively elevated, accompanied by a fine and uniform grain size in the Al layer. This situation decreases the likelihood of stress concentration at the interface, which results in exhibiting relatively optimal elongation and bonding strength.

Achieving significant grain refinement efficiency in Mg-Al alloys via a GNP@MgO composite refiner

Master alloys containing Zirconium (Zr) serve as effective grain refiners in most commercial cast magnesium (Mg) alloys. However, their efficacy is diminished in Mg–Al series alloys due to the formation of Al–Zr compounds. In this work, a novel Mg-GNP@MgO master alloy was prepared utilizing the in-situ reaction between CO2 and Mg. The grain refinement efficiency of this composite inoculation on Mg–9Al alloys was systematically investigated using SEM-EBSD, HRTEM observations, Density Functional Theory (DFT), and Sharp Interface Model (SIM) calculations. The findings suggest that the composite grain refiner (GNP@MgO) exerted a notable refining influence on Mg–9Al alloy. Through the conventional casting process, the average grain size was refined to approximately 13 μm upon the addition of 3 vol% GNP@MgO, achieving a grain refinement efficiency of 90 %. The enhanced refining efficiency arises from the synergistic control over the nucleation and growth processes of α-Mg grains, facilitated by GNP@MgO particles. This process includes improved heterogeneous nucleation, triggered by the newly formed Al4C3 phases through the interaction between GNPs and Al element, followed by the limited expansion of α-Mg grains induced by the nano-sized MgO particles. The MgO particles predominantly gather around grain boundaries to establish stable nano-coating layers, thereby exerting a substantial Zener pinning effect. The pinning role played by the MgO nanoparticles was also verified by a sharp interface model. The findings in this work not only carve out a new avenue for the grain refinement of cast Mg–Al alloys but also inspire fresh perspectives for the development of novel grain refiners.

The Effect of Hatch Spacing on the Electrochemistry and Discharge Performance of a CeO2/Al6061 Anode for an Al-Air Battery via Selective Laser Melting

To improve the electrochemical activity and discharge performance of an aluminum-air (Al-air) battery, a commercial 6061 alloy (Al6061) was selected as the anode, and CeO2 was also added inside the anode to enhance its performance. The CeO2/Al6061 composite was prepared using selective laser melting (SLM) technology. The influence of hatch spacing on the forming quality, corrosion resistance, and discharge performance of the anode was studied in detail. The results showed that with an increase in hatch spacing, the density, corrosion resistance, and discharge performance of the anode first increased and then decreased. When the hatch spacing is 0.13 mm, the anode has the best forming quality. At this point, the density reaches 98.39%, and the self-corrosion rate (SCR) decreases to 2.596 × 10−4 g·cm−2·min−1. Meanwhile, the anode exhibits its highest electrochemical activity and discharge voltage, which is up to −1.570 V. The change in anode performance is related to the defects generated during the SLM forming process. For samples with fewer defects, the anode can dissolve uniformly, while for samples with more defects, the electrode solution is prone to penetrate the defects, causing uneven corrosion and reducing electrochemical and discharge activity.