Aluminum-alumina Composites Research Articles

Insights into morphology and mechanical properties of architected interpenetrating aluminum-alumina composites

Additive manufacturing (AM) technologies are unleashing the restrictions imposed by conventional manufacturing, allowing the production of innovative designs tailored to improve properties or performance. AM techniques in ceramic production allow the application of novel designs to ceramic parts, opening new opportunities for combining technologies aiming to obtain architected interpenetrating phase composites (IPCs). In this study, alumina structures with different architectures and Computer Aided Design (CAD) structure porosity oriented unidirectionally or bidirectionally, were fabricated by vat photopolymerization technique, namely Digital Light Processing. Afterwards, these structures were infiltrated with an aluminum alloy through investment casting, thus obtaining aluminum-alumina IPCs. Under compression, the IPCs presented a ductile behavior, conversely to the fragile ceramic counterparts. The IPCs compressive strength and absorbed energy were expressively higher than their ceramic counterparts. Comparing the bidirectional IPCs with the unidirectional ones, a significant increase in compressive strength and absorbed energy was observed, from 36.2% to 42.3% and from 164.8% to 358.1%, respectively, due to the greater amount and interconnection of the metal inside the ceramic structure. This study demonstrates the feasibility of this manufacturing route, combining two distinctive technologies, for the fabrication of metal-ceramic architected IPCs, allowing to tailor their mechanical properties and energy absorption capacity for a given application.

Aluminum-Alumina Composite Manufacturing: Unlocking Potential with Friction Stir Processing

This study investigates the manufacturing of Aluminum-Alumina composites through Friction Stir Processing (FSP) and explores the resultant enhancements in mechanical properties. A key focus lies on achieving a uniform distribution of Al2O3 particles within the composite matrix, crucial for optimizing material performance. These dispersed particles act as effective strengthening agents, impeding dislocation movement and grain boundary migration, consequently improving mechanical attributes such as hardness, strength, and wear resistance. Experimental findings underscore the efficacy of FSP in enhancing various mechanical properties of the composite. Notably, significant improvements were observed, including a 23.56% increase in tensile strength, a 37.9% enhancement in hardness, a 25.5% improvement in fatigue strength, and a notable 30.12% increase in wear resistance. These results underscore the potential of Aluminum-Alumina composites manufactured via FSP to unlock new opportunities for high-performance materials in industries requiring superior mechanical properties and wear resistance, such as aerospace, automotive, and manufacturing sectors.

Mechanical and Thermal Properties of Aluminum Matrix Composites Reinforced by In Situ Al2O3 Nanoparticles Fabricated via Direct Chemical Reaction in Molten Salts

The development of novel methods for industrial production of metal-matrix composites with improved properties is extremely important. An aluminum matrix reinforced by “in situ” α-Al2O3 nanoparticles was fabricated via direct chemical reaction between molten aluminum and rutile TiO2 nanopowder under the layer of molten salts at 700–800 °C in air atmosphere. Morphology, size, and distribution of the in situ particles, as well as the microstructure and mechanical properties of the composites were investigated by XRD, SEM, Raman spectra, and hardness and tensile tests. Synthesized aluminum–alumina composites with Al2O3 concentration up to 19 wt.% had a characteristic metallic luster, their surfaces were smooth without any cracks and porosity. The obtained results indicate that the “in situ” particles were mainly cube-shaped on the nanometer scale and uniform matrix distribution. The concentration of Al2O3 nanoparticles depended on the exposure time and initial precursor concentration, rather than on the synthesis temperature. The influence of the structure of the studied materials on their ultimate strength, yield strength, and plasticity under static loads was established. It is shown that under static uniaxial tension, the cast aluminum composites containing aluminum oxide nanoparticles demonstrated significantly increased tensile strength, yield strength, and ductility. The microhardness and tensile strength of the composite material were by 20–30% higher than those of the metallic aluminum. The related elongation increased three times after the addition of nano-α Al2O3 into the aluminum matrix. Composite materials of the Al-Al2O3 system could be easily rolled into thin and ductile foils and wires. They could be re-melted for the repeated application.

Correction to: A Comparative Study of Mechanical Properties, Thermal Conductivity, Residual Stresses, and Wear Resistance of Aluminum-Alumina Composites Obtained by Squeeze Casting and Powder Metallurgy

Correction to: A Comparative Study of Mechanical Properties, Thermal Conductivity, Residual Stresses, and Wear Resistance of Aluminum-Alumina Composites Obtained by Squeeze Casting and Powder Metallurgy

High strength particulate aluminum matrix composite design: Synergistic strengthening strategy

Aluminum-alumina (Al–Al2O3) composites with ultrahigh strength were designed by combining dispersion strengthening via the addition of Al2O3 particles and matrix strengthening via in situ strain hardening. Cold spraying additive manufacturing technology was applied to fabricate the composites. The yield strength (σ0.2%) of the Al-46 wt% Al2O3 composite was 317.4 MPa and was among the highest value reported in the literature, to the best of our knowledge, for a pure Al-based Al–Al2O3 composite. Experimental evaluation of the material showed that the compressive failure mode of the composite changed from gradual plastic collapse to shear-dominated behavior as the percentage of Al2O3 was increased or the matrix was pre-strain strengthened in the Al–Al2O3 composite.

Experimental Investigation on Two-Body Abrasion of Cast Aluminum–Alumina Composites: Influence of Abrasive Size and Reinforcement Content

Abstract The occurrence of abrasion is inevitable in most engineering systems. Abrasive wear specifically two-body causes higher material and dimensional loss than other modes of wear. Two-body abrasion is yet to be fully comprehended as it is governed by several intrinsic and extrinsic variables. In this article, tribo-performances of Al-composites were experimentally studied with specific emphasis on the role of abrasive size and amount of reinforcement. AA7075 alloy matrix composites with different amounts of alumina particles were fabricated by the advanced stir-casting method. Besides measurements of density, porosity, and Vickers hardness, in-depth characterizations of microstructures were performed. Specific wear-rate (SWR), coefficient of friction (COF), and abraded surface roughness (SR) of developed materials were measured under two-body abrasion over a vast range of distance, load, velocity, and abrasive size. Under all abrasion conditions, composites exhibited higher SR but lower SWR and COF over alloy; the differences increased with reinforcement quantity. SWR, COF, and SR rose with an increase in abrasive size; however, only SR varied with sliding distance for any material. The effects of different variables on the recorded tribo-performances were explained through identification of various micro-mechanisms of abrasion via extensive post wear characterizations and microstructural features. Finally, the criteria for the occurrence of three-body abrasion even in two-body test configuration were highlighted. The wear coefficient value of 10 × 10−3 was identified as the demarcation between two-body and two-body plus three-body abrasion for Al-matrix composites.

Aluminum–Alumina Composites: Part Ⅰ: Obtaining and Characterization of Powders

The process of advanced aluminum-alumina powders production for selective laser melting was studied. The economically effective method of obtaining aluminum-alumina powdery composites for further selective laser melting was comprehensively studied. The aluminum powders with 10–20 wt. % alumina content were obtained by oxidation of aluminum in water. Aluminum oxidation was carried out at ≤200 °C. The oxidized powders were further dried at 120 °C and calcined at 600 °C. Four oxidation modes with different process temperatures (120–200 °C) and pressures (0.15–1.80 MPa) were investigated. Parameters of aluminum powders oxidation to obtain composites with 10.0, 14.5, 17.4, and 20.0 wt. % alumina have been determined. The alumina content, particle morphology, and particle size distribution for the obtained aluminum-alumina powdery composites were studied by XRD, SEM, laser diffraction, and volumetric methods. According to the obtained characteristics of aluminum-alumina powdery composites, they are suitable for the SLM process.

Effect of microstructure on mechanical properties and residual stresses in interpenetrating aluminum-alumina composites fabricated by squeeze casting

Aluminum-alumina composites with interpenetrating network structure are interesting structural materials due to their high resistance to elevated temperature and frictional wear, good heat conductivity, enhanced mechanical strength and fracture toughness. In this paper aluminum-alumina bulk composites and FGMs are manufactured by pressure infiltration of porous alumina preforms with molten aluminum alloy (EN AC-44200). Influence of the interpenetrating microstructure on the macroscopic bending strength, fracture toughness, hardness and heat conduction is examined. Special focus is on processing-induced thermal residual stresses in aluminum-alumina composites due to their potentially detrimental effects on material performance in structural elements under in-service conditions. The residual stresses are measured experimentally in the ceramic phase by neutron diffraction and simulated numerically using a micro-CT based Finite Element model, which takes into account the actual interpenetrating microstructure of the composite. The model predictions for two different volume fractions of alumina agree fairly well with the neutron diffraction measurements.

Processing Induced Flaws in Aluminum–Alumina Interpenetrating Phase Composites

This review paper deals with flaws in aluminum–alumina composites and FGMs induced by their manufacturing processes. Aluminum–alumina composites have been studied for many years as potentially interesting materials for applications, for example, in the automotive sector due to their enhanced mechanical strength, wear resistance, good heat conductivity and low specific weight. The focus here is on the interpenetrating phase composites (IPCs) manufactured by infiltration of porous alumina preforms with molten aluminum alloys. The primary objective is to provide an updated overview of research findings on a variety of flaws occurring at different stages of the manufacturing processes. Some precautions on how to avoid processing induced flaws in aluminum–alumina bulk composites and FGMs are mentioned.

Considerations Regarding Wetting Conditions in Aluminium-Alumina Composites

The mechanical and physical properties of metallic composites with aluminium matrix and alumina particles as complementary material have made them a good candidate for automotive, aerospace and many other applications. Some calculus regarding main aspect of wetting conditions between aluminium and alumina are made by using special literature information. Also, some improvement techniques of wetting conditions are described.

Mechanics of hot pressed aluminum composites

Aluminum powder with an average particle size of 10 μm was mechanically mixed thoroughly with 5 wt% fine Al2O3 powder with an average particle size of 3.7 μm reinforcement. Iron particles with an average particle size of 0.5 nm and copper particle size of 10 μm were added to the base matrix Al–5Al2O3. The composite material was produced by a single action hot compaction of the powders. Aluminum–alumina composites containing iron, copper, and iron with copper were produced through mixing the atomized matrix alloy powder with 5 wt% of Al2O3 particles, then cold pressed for 5 min, degaussed, and hot pressed. The hot pressing technique was performed up to 500 °C at 318.34 MPa for 5 min dwell time. The Al–5Al2O3 composites were examined for hardness, compression flow properties, and wear analysis.

The effect of microstructural morphology on the elastic, inelastic, and degradation behaviors of aluminum–alumina composites

Micromechanical models with idealized and simplified shapes of inhomogeneities have been widely used to obtain the average (macroscopic) mechanical response of different composite materials. The main purpose of this study is to examine whether the composites with irregular shapes of inhomogeneities, such as in the aluminum–alumina (Al–Al2O3) composites, can be approximated by considering idealized and simplified shapes of inhomogeneities in determining their overall macroscopic mechanical responses. We study the effects of microstructural characteristics, on mechanical behavior (elastic, inelastic, and degradation) of the constituents, and shapes and distributions of the pores and inclusions (inhomogeneities), and thermal stresses on the overall mechanical properties and response of the Al–Al2O3 composites. Microstructures of a composite with 20% alumina volume content are constructed from the microstructural images of the composite obtained by scanning electron microscopy (SEM). The SEM images of the composite are converted to finite element (FE) meshes, which are used to determine the overall mechanical response of the Al–Al2O3 composite. We also construct micromechanics model by considering circular shapes of the inhomogeneities, while maintaining the same volume contents and locations of the inhomogeneities as the ones in the micromechanics model with actual shapes of inhomogeneities. The macroscopic elastic and inelastic responses and stress fields in the constituents from the micromechanics models with actual and circular shapes of inhomogeneities are compared and discussed.

On characterizing the mechanical properties of aluminum–alumina composites

The overall response of aluminum–alumina (Al–Al2O3) composites depends strongly on their microstructural characteristics. We study the overall mechanical response of Al–Al2O3 composites experimentally, using Resonant Ultrasound Spectroscopy (RUS) and uniaxial compressive testing. Microstructures of composite with 10% alumina volume content are constructed from the microstructural images of the composite obtained from scanning electron microscopy (SEM). The SEM images of the composite are converted to finite element (FE) meshes, which are used to solve the boundary value problem in order to determine the overall mechanical response of the Al–Al2O3 composite. The responses generated from the micromechanical models are compared with the elastic modulus obtained from RUS and experimental stress–strain curves from uniaxial compression tests. Effects of processing, porosity, alumina content, thermal (residual) stress, and plastic deformation on the overall elastic modulus and response of the composites are also studied. We observed that slightly altering the processing method had a significant effect on the microstructural characteristics and in turn on the overall physical and mechanical properties of the composite. With changes in porosity by 2–3%, the elastic modulus was found to vary by 10–15GPa approximately. We observed that the elastic moduli of the composites determined from the uniaxial compressive tests are close to those obtained from RUS.

In Situ 3D Synchrotron Imaging of Failure Processes in Engineering Materials

The micrometer range resolution of Synchrotron Radiation Tomography has developed an important technique for characterizing the three dimensional (3D) microstructure of materials. This technique was used for imaging Aluminum-alumina composites, porous aluminum and AA 6061 alloy under different loading conditions. The experimental set-up was installed at the Biomedical Imaging and Therapy (BMIT)'s 05B1-1 beamline at Canadian Light Source (CLS). The experimental stage has been designed for conducting the in-situ experiments. The unique feature of this experimental stage is that the sample can be rotated torsion free for taking the images for Computed Tomography imaging during any loading conditions. The developed experimental system and technique allows deciphering the internal structures of composites, porous materials, multiphase alloys and to observe the failure processes such as crack initiation, crack propagation, void formation, void coalescence and the fracture process during loading of materials.

Development of texture during ARB in metal matrix composite

In the present study, the accumulative roll bonding (ARB) process was used as a technique for manufacturing aluminium–alumina composites. Textural evolution during the ARB process of composites was evaluated using X-ray diffraction. After the first ARB cycle, copper {112}〈111〉 and brass {011}〈211〉 were the major texture components. However, with the progress of deformation after 5 cycles, the components transformed completely, and the rotated cube {001}〈110〉 component became dominant, which remained as the major component in higher cycles (ninth and thirteenth). This shear texture was developed due to the shear deformation induced by the high level of friction between the rolls and the strips. Generally, the intensity of all the texture components, except that of the rotated cube, was very weak. This result is attributed to the presence of second phase particles.

Analysis of Dry Sliding Friction and Wear Behavior of Aluminum-Alumina Composites using Taguchi’s Techniques

Metal-matrix composites (MMCs) are attracting considerable interest worldwide because of their superior mechanical and tribological properties. This study describes multifactor-based experiments that were applied to research and investigation on dry sliding wear system of stir cast Al-Si10Mg matrix alloy with 5 and 10 wt% alumina-reinforced MMCs. The effects of parameters like load, sliding speed, percentage of alumina on the dry sliding wear, and friction coefficient of aluminum MMCs using Taguchi’s method are reported. An orthogonal array (L27) and analysis of variance were used to investigate the influence of parameters like normal load, sliding speed, and reinforcement percentage and their interactions on dry sliding wear and friction coefficient of the composites. The major objective was to investigate the parameter that significantly affects the dry sliding wear and friction coefficient. The results show that friction coefficient and wear rate were highly influenced by load, sliding speed, and percentage of alumina whereas the interactions between these parameters, show only a minor influence in MMCs. The worn surfaces of the pins were then analyzed by scanning electron microscopy to study the wear mechanism and to correlate them with wear test results.

Preparation of interpenetrating ceramic–metal composites

Ceramic reinforced metals are attractive because of their enhanced elastic modulus, high strength, tribological properties and low thermal expansion. Most work in this sector has focused on particle- or fiber-reinforced composites where the ceramic phase is not continuous. This work presents aluminium–alumina composites where both phases are interpenetrating throughout the microstructure. Ceramic preforms were produced with sacrificial pore forming agents leading to porosities between 50% and 67%. Pore wall microstructure was varied by changing the sintering temperature. Permeability and strength was measured for the porous preforms and infiltration results were compared with theoretical predictions based on capillary law and Darcian flow. A direct squeeze-casting process was used to infiltrate the preforms with aluminium resulting in an interpenetrating microstructure on both macropore and micropore scale.

Dry sliding wear behavior of Al 2O 3 fiber reinforced aluminum composites

Dry sliding wear behavior of die-cast ADC12 aluminum alloy composites reinforced with short alumina fibers were investigated by using a pin-on-disk wear tester. The Al 2O 3 fibers were 4 μm in diameter and were present in volume fractions ( V f) ranging from 0.03 to 0.26. The length of the fiber varied from 40 to 200 μm. Disks of aluminum–alumina composites were rubbed against a pin of nitrided stainless steel SUS440B with a load of 10 N at a sliding velocity of 0.1 m/s. The unreinforced ADC12 aluminum alloy and their composites containing low volume fractions of alumina ( V f ≈ 0.05) showed a sliding-distance-dependent transition from severe to mild wear. However, composites containing high volume fractions of alumina ( V f>0.05) exhibited only mild wear for all sliding distances. The duration of occurrence of the severe wear regime and the wear rate both decrease with increasing volume fraction. In MMCs the wear rate in the mild wear regime decreases with increase in volume fraction, reaching a minimum value at V f=0.09. Beyond V f=0.09 the wear rate increases marginally. On the other hand, the wear rate of the counterface (steel pin) was found to increase moderately with increase in V f. From the analysis of wear data and detailed examination of (a) worn surfaces, (b) their cross-sections and (c) wear debris, two modes of wear mechanisms have been identified to be operative, in these materials and these are: (i) adhesive wear in the case of unreinforced matrix material and in MMCs with low V f and (ii) abrasive wear in the case of MMCs with high V f.

Mechanical properties and wear strengths in aluminium-alumina composites

In this study, after producing metal matrix composite materials reinforced with ceramic particles by adding hard Al2O3 particles into a selected ageable aluminum alloy, the wear strengths were investigated. Composites of aluminum alloys containing 2 to 10 wt of Al2O3 particles in the size range of 23.4 to 108 μm were prepared by adding alumina particles to a partially-solid vigorously-agitated matrix alloy. For a given tribologic system, the sizes and ratios of optimum particles were determined from the point of the wear strengths of these materials, of which the wear strengths greatly increased according to the matrix materials. Alumina particles were subjected to preheating at 500°C for 8 hours. Particles were added into the alumina alloy heated up to semi-solid/semi-liquid phase interval in an argon medium by using a mixer. Then furnace temperature was raised up to 800°C step by step. Later the composite materials were die cast and solidified and aged. The behavior of the composites was studied by using a pin-on-disk type machine. The largest wear strengths were obtained at an average particle size of 76.5 μm and percentage of 4% wt Al2O3. Increase in the wear strength of the composites was obtained as 3.85 times the wear strength of the matrix material.

Composite solid armature consolidation by pulse power processing: a novel homopolar generator application in EML technology

Graded electrical resistance and assured sliding contact are among the desirable characteristics for the solid armatures used in railguns attainable through the use of composite materials. Metal-metal, metal-ceramic, and metal-polymer composites are generic types of potential solid armature materials. The authors describe the production of these composites by a novel experimental approach that uses a homopolar generator in a pulse-powered materials consolidation system. The processing of copper-tungsten and aluminium-alumina composites is used to demonstrate versatility of the homopolar generator as a materials processing tool. Powder metallurgy and laminate bonding approaches have been utilized. Composite solid armature materials have been consolidated with subsecond high-temperature exposure. Densification in the solid state proceeds by a warm/hot forging mechanism, and fully dense composites are obtained by a combined application of pressure and a controlled energy input.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>