Al Matrix Research Articles

İndüksiyonla sıcak işlemin Si3N4 ve grafen takviyeli Al6061 matrisli kompozitlerin mekanik ve tribolojik özelliklerine olan etkisi

Yapılan bu çalışmada indüksiyonla sıcak presleme ve toz metalürjisi yöntemleri ile Al6061 matrisli Si3N4 (ağırlıkça %1-12) ve grafen (ağırlıkça %0,15-0,45) takviyeli kompozitler üretilmiştir. Üretilen kompozit malzemelerin yoğunluğu, sertliği, basma dayanımı, aşınma direnci, mikroyapısı ve faz yapısı sırasıyla incelenmiştir. Yapılan testler sonucunda en yoğun mikroyapı, en iyi mekanik ve tribolojik özellikler Al6061-%9Si3N4-%0.15grafen kompozit yapıda elde edilmiştir. Yürütülen ısıl işlem çalışmaları neticesinde ise; sinterleme sonrası indüksiyonla sıcak preslenmiş numunelerin mekanik ve tribolojik özelliklerinin yalnızca sinterlenmiş kompozitlere kıyasla ~%37’ye varan oranlarda iyileştiği tespit edilmiştir.

Achieving exceptional strength by multi-dimensional in-situ Al3Ti, TiN, AlN reinforcements in Al matrix composites

Despite the high demand for strong, lightweight, and tough Aluminum Matrix Composites (AMCs) across various applications, achieving desired property compatibility remains challenging due to limited control over the reinforcement processes. A novel AMC has been developed and synergistically reinforced with transgranular microscale Al3Ti, sub-microscale TiN, and intergranular nanoscale AlN, through Ti2AlN and Al in situ reaction. The in-situ multiphase-and-scale structure, resulting from the intricate reaction mechanisms and N interstitial solution, was analyzed using experimental investigations, thermodynamics and kinetics calculations, while the robust interfacial properties were studied by first-principles calculations. Both endowed the composite with exceptional strength (776 MPa and 635 MPa for compressive and flexural strength). Strengthen mechanisms were composed of fine-grain, solid-solution, and dislocation strengthening. This work succeeds in refining Al3Ti particles and creatively breaks through the bottleneck of synthesizing multi-dimensional and tunable in-situ reinforcements, expected to open new avenues for developing and applying a new generation of advanced AMCs.

Tribological Properties of Aluminium Matrix Syntactic Foams Manufactured with Aluminium Smelter Waste

Aluminium smelter waste (ASW) is a big contributor to landfills, and its recycling has been of great interest. This study investigates the tribological properties of aluminium matrix syntactic foams manufactured using an Al 6082 alloy and ASW. Ball-on-disc tests were conducted under both dry and lubricated conditions. Under dry sliding conditions, the coefficient of friction (COF) had an initial sharp increase, followed by a gradual decrease and finally a steady state as the sliding distance increased. The wear surfaces showed the presence of adhesive, abrasive and oxidative wear, with some presence of delamination. Syntactic foams containing small ASW particles led to a decrease in surface roughness, decrease in the average COF and decrease in specific wear. Heating large ASW particles before manufacturing the syntactic foams enhanced overall wear properties because the particles are hardened due to a compositional change. The T6 treatment of the syntactic foams enhanced the wear properties due to the hardening of the Al matrix. The average COF of the ASW syntactic foams was higher than that of the E-sphere syntactic foam, which was predominantly abrasive wear. The specific wear of the ASW syntactic foams can be higher or lower than the E-sphere syntactic foam, depending on the ASW particle size. Under lubricated sliding test conditions, the wear was reduced significantly, and the type changed from predominantly adhesive to predominantly abrasive. The porous ASW particles acted as lubricant reservoirs and provided a constant supply of lubricant, further improving the lubrication effect.

Effect of SiC particle content on the mechanical behavior and deformation mechanism of SiCp/Al composite under high-frequency dynamic loading

SiCp/Al composites exhibit excellent structural properties but suffer from inherent brittleness, which has brought rigorous challenges on the materials processing. Ultrasonic-vibration-assisted approach offers a promising solution to improve the processability. However, the underlying mechanisms of mechanical response and defect suppression under ultrasonic action have been rarely studied for SiCp/Al composites, hindering the development of high-efficiency processing. This work aims to investigate the mechanical behavior and microstructural evolution in this class of composites with varying SiC volume fractions up to 45% under high-frequency dynamic load induced by ultrasonic vibration. The results showed that the deformation stress of SiCp/Al composites under ultrasonic compression was significantly reduced to only about 1/10 of that under conventional quasi-static loading. Moreover, as the SiC fractions increasing, this ultrasonic softening effect of SiCp/Al became more pronounced. The plastic limit of SiCp/Al with 45% SiC fraction nearly doubled under ultrasonic compression without any macroscopic cracks. The subsequent nanoindentation tests revealed a transition in work-hardening behavior of SiCp/Al with different SiC fractions under ultrasonic loading. Microstructure characterization was conducted to analyze the grain refinement, recrystallization, and deformation textures within the deformed areas, revealing the deformation mechanism of SiCp/Al under different loading mode. TEM observations confirmed the distribution of dislocations in Al matrix and dense stacking faults in SiC particles after ultrasonic compression, indicating that the plastic behaviors were enhanced in both Al matrix and SiC phase under the high-frequency cyclic stress. This research revealed the distinct deformation mechanisms of SiCp/Al composites under high-frequency dynamic loading, exhibiting extremely low deformation stress accompanied with significantly enhanced plasticity. The results provide theoretical insights for the high-efficiency processing and rapid property regulation of particle-reinforced-composites based on ultrasonic-vibration-assisted technologies.

Preparation, Microstructure, and Mechanical Properties of Al Matrix Composites Reinforced with High‐Entropy Alloys: A Review

Al matrix composites (AMCs) are innovative materials prepared by introducing various reinforcements into Al alloys using suitable processes. Traditional particle‐reinforced AMCs usually have high strength but poor interfacial bonding, resulting in low plasticity. Researchers are attempting to solve this problem by identifying more proper reinforcing particles. High‐entropy alloys (HEAs) with excellent mechanical properties including high strength, ductility, and wear resistance are becoming attractive candidates for the reinforcement of Al alloys. The HEAs‐reinforced AMCs (HEAs@AMCs) combine the lightweight property of Al alloys and superior mechanical properties of HEAs. In this article, a comprehensive overview is provided on the HEAs@AMCs, starting with an introduction to the properties of HEAs, followed by the design principle of HEAs for the metal matrix composites. After that, the preparation, microstructure, and mechanical properties of the HEAs@AMCs are examined. In addition, the effects of HEAs on the microstructure and mechanical properties of the HEAs@AMCs are explored.

Field-assisted sintering of high-entropy alloy-reinforced aluminium matrix composites: phase identification and microstructural properties

This study investigates the design, phase identification, and microstructural properties of high-entropy alloy (HEA)-reinforced aluminium (Al) matrix composites. Thermophysical expressions for HEAs were employed during the design phase of the HEA; both theoretical frameworks and experimental analyses were used to anticipate stable phases while a field-assisted sintering technique was employed to consolidate the samples. Calculation of phase diagram (CALPHAD) predictions for the phases present in the HEA align with valence electron concentration (VEC) calculations as both predicted the presence of BCC and FCC phases. The microhardness results reveal a substantial increase in the hardness value of the composites as compared to the pure Al, such that as low as 5 wt% HEA addition resulted in over a 100% improvement, while the densification of the composites was found to decrease with an increase in the wt% of HEA. SEM micrographs and XRD analyses show fair dispersion, bonding, and phase integration in the HEA-reinforced composites.

Nano-Al2O3 Particle Incorporated in Al Matrix Composite by Vortex-Free High-Speed Stir Casting

Nano-Al2O3 Particle Incorporated in Al Matrix Composite by Vortex-Free High-Speed Stir Casting

Corrosion resistance of additively manufactured aluminium alloys for marine applications

Additive manufacturing opens new possibilities for designing light-weight structures using aluminium alloys. The microstructure of two Al alloys and their corrosion resistance in NaCl and natural seawater environments were investigated. The newly designed Al-Mn-Cr-Zr based alloy showed a higher corrosion resistance than reference AlSi10Mg alloy in both environments in as printed and heat-treated conditions. The corrosion initiated in the Al matrix along the precipitates in the alloys where the Volta potential difference was found the highest. The coarser microstructure and precipitate composition of the new Al-alloy led to the formation of a resistant passive film which extended the passivity region of the Al-Mn-Cr-Zr alloy compared to the AlSi10Mg alloy. The effect of heat treatment could be seen in the microstructure as more precipitates were found in between the melt pool boundaries, which affected the corrosion initiation and slightly the pitting resistance. Overall, this study shows that a newly designed Al-alloy for additive manufacturing has a suitable corrosion resistance for applications in marine environments.

Unraveling L12 Al3X (X=Ti, Zr, Hf) nano-precipitate evolution in aluminum alloys via multi-scale diffusion simulation

The evolution of L12 Al3X (X = Ti, Zr, Hf) nano-precipitates in Al-X alloys was studied by multi-scale diffusion simulation using a combination of first principles calculation and finite element method. The results show that the diffusion coefficient in Al-X solid-solution phase follows DAl>DZr>DHf>DTi, which are in excellent agreement with available experimental values. On the other hand, the mobility of X atoms in L12 Al3X phases is reversed, following DAlAl3X>DTiAl3Ti>DHfAl3Hf>DZrAl3Zr. The calculated Al and X diffusion coefficients in both Al-X solid-solution and L12 Al3X ordered phases were used to simulate the evolution of L12 nano-precipitate embedded in Al-X solid-solution matrix. It is found that only Zr could promote the formation of nano-precipitates at 650 K, the common heat-treatment temperature for advanced Al alloys. At lower temperature, the sluggish atomic movement hinder the nucleation of L12 phase, while at higher temperature the precipitates redissolve into the Al matrix. The multi-scale diffusion simulation underlines the indispensable role of diffusion in L12 Al3X phases on the nano-precipitate evolution, and also provides a feasible way to the rationally design of precipitate strengthening alloys.

Microstructure evolution and mechanical properties of high-performance Al–Mn–Mg–Sc–Zr alloy fabricated by laser powder bed fusion

The influence of aging temperatures on the microstructure and mechanical properties of an Al–Mn–Mg– Sc–Zr alloy prepared by laser powder bed fusion (L-PBF) was systematically studied. The results show that the fabricated alloy was a dense and crack-free piece with a fine grain size of 3.51 μm and a yield strength of (547±3) MPa. When the alloy was subjected to aging at 300 °C, a large amount of highly coherent Al3Sc nanoparticles (2–3 nm) precipitated from the Al matrix. The aged sample exhibited a high yield strength of (616±4) MPa, which can be attributed to precipitation strengthening, solid solution strengthening, and grain boundary strengthening. When the alloy was aged at a temperature higher than 300 °C, part of the dissolved Mn and Zr precipitated in the form of Al6Mn and Al3(Sc,Zr). When the alloy was aged at 500 °C, the Al6Mn and Al3(Sc,Zr) precipitates grew to approximately 600 and 30 nm, respectively, in size. Consequently, the yield strength of the alloy decreased to (372±3) MPa.

Preparation of SiC/Al composite material by supergravity infiltration method and its properties

SiC/Al composite materials with SiC particle sizes of 23, 48, and 150 μm were successfully prepared using the supergravity infiltration method. Engineering scale-up experiments were performed to validate this method. This approach not only achieved near-final shaping of SiC/Al composite materials but also prevented adverse interfacial reactions between the Al matrix and SiC particles due to the low preparation temperature and fast speed. Increasing the gravity coefficient resulted in higher centrifugal pressure, thereby enhancing the relative density of the SiC/Al composite materials. At a gravity coefficient of G=1000, the relative density of SiC/Al composite materials with reinforcement particle sizes of 48 and 150 μm exceeded 99.6 %. Additionally, when the gravity coefficient G is 1000, it only takes 0.02 s for the Al liquid to completely infiltrate a 2 cm SiC preform. The supergravity method significantly accelerates the infiltration speed of Al liquid.

Fabrication of TiB2/6061Al composite with tailoring heterostructure and superior mechanical properties and investigation on deformation behaviors

Overcoming the trade-off between strength and ductility remains a critical challenge for Al matrix composites. Here, TiB2/6061Al composites with harmonic and lamellar heterostructures were fabricated via hot press sintering by altering the size of Al powders. The discontinuous dynamic recrystallization (DDRX) and DRX take place, with DDRX being particularly promoted by the presence of fine grains around coarse grains. The activated slip systems of the grains with similar orientations are nearly identical during tension, while those of the randomly orientated grains vary significantly. Geometrically necessary dislocations form in fine grains due to their limited deformation compatibility, and also in the boundaries between fine and coarse grains. The heterostructured composite exhibits a superior strength-ductility synergy compared to the homogeneous composite, attributed to the hetero-deformation induced strengthening and dislocation strengthening. Strain concentrates in fine-grain zones with TiB2 particles, while the strain concentration is alleviated in coarse-grain zones, contributing to a high elongation.

Processing of high-strength thermal-resistant Al-2.2% cerium-1.3% lanthanum alloy rods with high electric conductivity by High Pressure Torsion Extrusion

A novel severe plastic deformation (SPD) process of High Pressure Torsion Extrusion (HPTE) was applied to the rods of the Al-2.2 wt.% Ce-1.3 wt.% La (Al–3.5RE) alloy. The microstructure, microhardness, the mechanical strength, thermal stability, and electrical conductivity of the alloy after HPTE and subsequent annealing have been investigated. It was demonstrated that HPTE processing can simultaneously increase yield strength from 127 to 225 MPa and electrical conductivity from 54.7% IACS to 55.7% IACS in this alloy. Such a remarkable combination of properties was achieved thanks to significant refinement of microstructure constituents: grain size of Al matrix was reduced down to 0.9 µm and initially continuous network of Al11RE3 phase was broken to micrometer- and nanometer-sized particles. Furthermore, the yield strength of the HPTE-processed Al–3.5 RE alloy remains stable at 230 °C for 1 h due to micrometer- and nanometer-sized particles that pin the grain boundaries. Therefore, HPTE processing of Al–RE alloys has a high application potential in the electric power industry.Graphical abstract

High activity retention Al–Bi–Zn-base composite powder with mild hydrogen generation

Al–10Bi–7Zn and Al–10Bi–7Zn–1.5X (X: Cu, Fe, Ni, in wt.%) composite powders were designed and prepared through phase diagram calculation and gas atomization method. The effects of Cu, Fe, and Ni on the hydrolysis of Al–Bi–Zn-base composite powders for hydrogen production were investigated respectively. The composition and morphology of powders were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy disperse spectroscopy (EDS) analyses. Hydrolysis performance test results indicate that the additions of Cu, Fe, or Ni can modify the hydrogen production rate and enhance oxidation resistance in Al–10Bi–7Zn ternary alloy composite powder. In the quaternary composite powder system, Al–10Bi–7Zn–1.5Ni (wt.%) exhibits the best performance with the hydrogen generation yield of 75.3% (954.1 mL/g) within 500 min when reacting with distilled water at 60 °C and maintains a hydrogen yield of 57.9% (733.7 mL/g) within 1500 min after being stored (30 °C, relative humidity of 60%) for 7 d. In addition, the mechanism investigation suggested that the additions of Cu, Fe, or Ni in Al–Bi–Zn-base composite powders can stabilize the Al matrix to retain the high activity of powders resulting from inhibiting the cracking of composite powders in the air.

Controlled Size Characterization Process for In-Situ TiB2 Particles from Al Matrix Composites Using Nanoparticle Size Analysis.

The wide size range and high tendency to agglomerate of in-situ TiB2 particles in reinforced Al matrix composites introduce great difficulties in their size characterization. In order to use a nanoparticle size analyzer (NSA) to obtain the precise size distribution of TiB2 particles, a controlled size characterization process has been explored. First, the extraction and drying processes for TiB2 particles were optimized. In the extraction process, alternated applications of magnetic stirring and normal ultrasound treatments were proven to accelerate the dissolution of the Al matrix in HCl solution. Furthermore, freeze-drying was found to minimize the agglomeration tendency among TiB2 particles, facilitating the acquisition of pure powders. Such powders were quantitatively made into an initial TiB2 suspension. Second, the chemical and physical dispersion technologies involved in initial TiB2 suspension were put into focus. Chemically, adding PEI (M.W. 10000) at a ratio of mPEI/mTiB2 = 1/30 into the initial suspension can greatly improve the degree of TiB2 dispersion. Physically, the optimum duration for high-energy ultrasound application to achieve TiB2 dispersion was 10 min. Overall, the corresponding underlying dispersion mechanisms were discussed in detail. With the combination of these chemical and physical dispersion specifications for TiB2 suspension, the bimodal size distribution of TiB2 was able to be characterized by NSA for the first time, and its number-average diameter was 111 ± 6 nm, which was reduced by 59.8% over the initial suspension. Indeed, the small-sized and large-sized peaks of the TiB2 particles characterized by NSA mostly match the results obtained from transmission electron microscopy and scanning electron microscopy, respectively.

High entropy (HfTiZrVNb)B2 ceramic particulate reinforced Al matrix composites: Synthesis, mechanical, microstructural and thermal characterization

This study aims to introduce a novel type of particulate reinforced Al matrix composite. High entropy (HfTiZrVNb)B2 ceramic particulate reinforced Al matrix composites were produced via a combined process of different powder metallurgy methods. Firstly, boride compounds (HfB2, TiB2, ZrB2, VB2, NbB2) were synthesized in the laboratory scale using the related metal oxide, boron oxide, and magnesium by mechanochemical synthesis (MCS) and leaching processes under optimum conditions. Secondly, the synthesized and purified boride powders were mixed in equimolar ratios using a planetary ball mill for 72 h, and they were sintered at 2000 °C under 30 MPa via spark plasma sintering (SPS). Thirdly, equimolar high entropy (HfTiZrVNb)B2 bulks were crushed, converted into powder forms, and added into Al powders at different amounts as 1, 2, 5, 10, and 15 wt %. Lastly, these powder blends were mechanically alloyed in a vibratory ball mill for 6 h, cold pressed and pressureless sintered at 630 °C for 2 h. For characterization techniques, X-ray diffractometry (XRD), thermal analysis, scanning electron microscopy/energy dispersive spectrometry (SEM/EDS), density measurements using pycnometer and Archimedes' methods, microhardness and dry sliding wear tests were conducted on the sintered composites. The highest hardness (∼1.5 GPa) and the lowest wear rate (∼0.0012 mm3/Nm) were obtained in the Al-15 wt % (HfTiZrVNb)B2 sample.

Nanoscale Al precipitation in the Si phase in AlSi10Mg alloy during electron beam powder bed fusion

Additive manufacturing of Al alloys has garnered attention in the aerospace and automobile industries. This is the first study on the formation of nanoscale Al precipitates in the Si phase of an AlSi10Mg alloy during electron beam powder bed fusion (EB-PBF). Spherical Si particles were homogeneously dispersed in the Al matrix, highlighting the difference from the laser beam PBF (LB-PBF) microstructures. Nanoscale Al phase was formed with a crystallographic orientation relationship with the surrounding Si phase: (111)Si//(111)Al and [11¯0]Si//[11¯0]Al. The formation of Al nanoprecipitates was attributed to an interplay between non-equilibrium solidification, wherein excess Al was dissolved in the Si particles, and the subsequent decomposition of the supersaturated Si phase during high-temperature exposure owing to the preheating procedure. To the best of our knowledge, such formation of Al nanoparticles has not been reported in AlSi10Mg produced through conventional processing or LB-PBF. Thus, the unique thermal history of EB-PBF provides novel opportunities for microstructural evolution, which may be beneficial for the development of novel Al-based alloys.

Heat-resistant super-dispersed oxide strengthened aluminium alloys.

Oxided-dispersion-strengthened (ODS) alloys are promising high-strength materials used in extreme environments such as high-temperature and radiation tolerance applications. Until now, ODS alloys have been developed for reducible metals by chemical processing methods, but there are no commercially available ODS alloys for unreducible metals, namely, Al, Mg, Ti, Zr and so on, owing to the challenge of uniformly dispersing oxide particles in these alloys by traditional techniques. Here we present a strategy to achieve ODS Al alloys containing highly dispersive 5 nm MgO nanoparticles by powder metallurgy, using nanoparticles that have in situ-grown graphene-like coatings and hence largely reduced surface energy. Notably, the densely dispersed MgO nanoparticles, which have a fully coherent relationship with an Al matrix, show effective suppression of interfacial vacancy diffusion, thus leading to unprecedented strength (~200 MPa) and creep resistance at temperatures as high as 500 °C. Our processing approach should enable the dispersion of ultrafine nanoparticles in a wide range of alloys for high-temperature-related applications.

Passivation and corrosion of Al current collectors in lithium-ion batteries

State-of-the-art lithium-ion batteries inevitably suffer from electrode corrosion over long-term operation, such as corrosion of Al current collectors. However, the understanding of Al corrosion and its impacts on the battery performances have not been evaluated in detail. The passivation, its breakdown, and corrosion of the Al resulted in the deterioration of the solid/solid interface and electrode integrity. Additionally, localized diffusion of F−/Al3+ brought the irreversible current detrimental to the Coulomb efficiency (1.14% loss). Eventually, the behavior led to extensive capacity damage (>20%) to battery performance until lifespan. During the battery cycling, the passivation layer greater than 20 nm was generated near the median voltage. When the charging voltage rose, the passivation layer was squeezed and deformed by the newly generated Al-F-O particles, resulting in stress corrosion cracks. The passivation layer peeled off, and the nano-passivation layer material was re-generated as the voltage continued to rise. The above results were repeated, and the Al matrix was continuously consumed. The passivity breakdown with localized corrosion was derived from ethylene carbonate adsorption, which was highly correlated to the charge voltages, especially at 4.4 V and 4.8 V. The results will serve as a benchmark for electrode corrosion of other advanced energy storage materials, which is crucial for electrode engineering and performance modulation using interfacial design.

Insight into the Fe-rich phases strengthening mechanisms of non-heat-treatable Al-Mg-Mn-Fe-Cu alloys

This paper examines the effect of Fe addition on the microstructure characterized by scanning electron microscopy/electron backscattered diffraction, neutron diffraction, and synchrotron X-ray tomography and the mechanical properties of Al-Mg-Mn-Fe-Cu alloys. The findings reveal that the microstructures of the alloys consisted of an Al matrix, Al6(FeMn), and Al2CuMg phase particles. The addition of Fe significantly increased the yield strength (YS), and ultimate tensile strength (UTS) of the alloys, while reducing elongation. The transformation of the 3D morphology of the Al6(FeMn) phase from separated and fine particles with Chinese-script morphology to interconnected rod-like structure as Fe content increased from 0.1 % to 0.8 %. This strengthening effect was attributed to the slip lines being blocked at the vicinity of the interconnected Fe-rich phase, leading to grain rotation and dislocation density increment around the Fe-rich phase, ultimately improving the strength of the alloys. However, the Fe-rich phases and Al2CuMg phases were found to be prone to cracking under tensile stress, resulting in decreased elongation of the alloys. This study provides a potential application in the design and manufacturing of new non-heat-treatable Al alloys for the automotive industry.