Aluminum-based Matrix Research Articles

Dissipative properties of Al-(Fe, Cr) vacuum coatings with different composite structures

Heterogeneous Al-(Fe, Cr) vacuum coatings were produced by electron beam vapor physical deposition (EB-PVD). It is shown that the composite structure (CS) of 85 at.% Al-(Fe, Cr) coatings consists of an aluminum-based matrix, strengthened by particles of λ-phase (CS-I), whereas that of 71 at.% Al-(Fe, Cr) coatings consists of fragmented grains of metastable bcc-phase and nano-sized particles of tetragonal Al(Cr, Fe)2 phase located along the boundaries of bcc-phase subgrains (CS-II). Effect of the different composite structures on their dissipative properties was studied. The coatings with the two types of CS have approximately the same microhardness, Hμ = 6–7 GPa, while their dissipative properties in the temperature range of 293–623 K are substantially different. It is found that the damping capacity (DC) for coatings with CS-II are 2–3 times higher than that of the coatings with CS-I(at strain amplitude of ε ~ 4 × 10−4). Moreover, CS-II coatings are characterized by the amplitude-dependent damping curves with a maximum, while CS-I coatings exhibit a monotonic increase with amplitude. These differences in the coatings DC may be related to the distinction of mechanisms of energy dissipation in them. In the case of CS-I coatings, the main dissipation mechanisms are dislocation processes and grain-boundary diffusion at elevated temperatures, whereas in the case of CS-II coatings it can be due to the friction of nano-cracks edges.

Development and investigations of Al5083/CNT/Ni/MoS2 metal matrix composite for offshore applications

Abstract Metal matrix composite (MMC) is one such material that can be produced to suite for low and high-temperature applications with various cyclic loads. The present research aims at the evolution of aluminium based metal matrix composite material reinforced with distinct weight percentage of CNT/Ni/MoS2 ceramics by traditional stir casting. Various mechanical and tribological characteristics were studied on the cast composites. The mechanical properties namely hardness, compression strength and ultimate tensile strength enhanced with an addition of ceramic particulate in the aluminium base matrix alloy in terms of weight percentage. Also an increment in weight percentage of reinforcement’s particulate influences the tribological and corrosion properties of the proposed composite material.

Al/SiCNP and Al/SiCNP/X nanocomposites fabrication and properties: A review

Global requirement for minimum cost, high efficiency, and good grade materials has made a diversion in research from base alloys to composite materials, since the last five decades. In the case of metal matrix composites, aluminium metal matrix composites have been certified and steadily advanced due to properties such as high strength, low density, and high wear resistance. They are widely used in automobile industry, aircraft industry, structural applications, and many other defence systems. Researchers have observed that the addition of nano-size SiCNP reinforcements to aluminium-based matrix yields superior properties and good bonding characteristics between matrix and reinforcements of nanocomposites. Along with silicon carbide particulate primary nano-reinforcements, researchers studied the properties of aluminium metal matrix nanocomposites with the addition of secondary reinforcements. These hybrid nanocomposites exhibited improved wear resistance. This article reviews the fabrication methods, mechanical properties, and tribological properties of aluminium-based hybrid metal matrix nanocomposites.

Investigation of Experimental Dispersion Fuel Elements with an Aluminum-Based Matrix for High-Flux Research Reactors

A variant of experimental dispersion fuel elements with fuel based on uranium dioxide as fissile material in a silumin matrix, which have been proposed for modernizing the core of the SM reactor and are irradiated in a wide spectrum of neutron-physical and thermophysical parameters in the reflector channel of the reactor, is investigated. A nonuniformity with fuel density two times higher than the average over a fuel element, viz., a cluster of uranium dioxide particles in the central zone of the kernel, has been found in the distribution of the fuel phase in the fuel elements. The thermophysical calculations show that for such a distribution of fuel particles the temperature of the fuel composition with heat flux density from the fuel-element surface >6 MW/m2 can reach the melting temperature of the matrix. This is confirmed by investigations of fuel elements with appreciably larger volume and shape change. To increase the serviceability of the fuel elements, ways of improving their design and the material composition of the fuel mix are proposed.

Microstructural changes in quasicrystalline Al–Mn–Be–Cu alloy after various heat treatments

Abstract In this study we investigated the microstructural changes after a variety of heat treatments of the quasicrystalline Al–Mn–Be–Cu alloy. In addition, we report on Vickers microhardness measurements and tensile-test results for the same materials. The samples were produced in a conventional manner, i. e., melting in an electrical resistance furnace in air and a gravitational casting process using a round copper die, which was in the form of a tensile-test specimen with a diameter of 5 mm. After the casting, some of the samples were just solution treated (annealed) and then quenched in water, while others were additionally aged (artificially – T6, or naturally – T4) or directly aged after the casting. In comparison to the as-cast state, the Vickers microhardness values of the aluminum-based matrix and the tensile properties of the samples decreased when just the solution treatment, T4 or T6 treatment was performed. The tensile properties also decreased after the heat treatments. A microstructural inspection revealed that the microstructural changes occurred already during the solution treatment, i. e., the formation of the phases Be4Al(Mn, Cu) and τ1-Al29Mn6Cu4 on the approximant H-Al4Mn and quasicrystalline i-phase particles' edges and the occurrence of precipitates in the αAl matrix. The precipitates that would additionally contribute to the hardening of the alloy did not form. The directly aged samples showed little or no increase in microhardness values in comparison to the as-cast samples, but possibilities of θ″ precipitates being formed from the already saturated matrix after the casting could not be excluded. After all the heat treatments the quasicrystalline i-phase, as a primary and eutectic phase, was preserved.

Effect of Aeration on the Microelectrochemical Characterization of Al[sub 2]Cu Intermetallic Phases

Local probing of the galvanic coupling between micrometer-sized Al 2 Cu phases and the surrounding aluminum-based matrix of a specially heat-treated 2011 alloy is investigated using a microcapillary electrochemical cell. The aging of an isolated Al 2 Cu particle, i.e., selective dissolution of aluminum, is controlled by the aeration condition at the tip of the capillary due to the nature of the silicon membrane used as a gasket. The local electrochemical behavior of an isolated particle after aging confirms the mass transport control of the oxygen reduction on the galvanic coupling of the particle with the surrounding matrix.

Modifying aluminum-based matrix structures by cathodic insertion

The effect of the temperature of a phosphate treatment on the kinetics of subsequent cathodic insertion of lanthanum and lithium is studied. The effect of the temperature on the processes of cathodic insertion of lanthanum and lithium into Al(phosphate) and LaAl(phosphate)—electrodes at the stages of the formation of, respectively, a solid solution and an intermetallic compound—is studied.

A methodology for the prediction of standard steady-state wear coefficient in an aluminium-based matrix composite reinforced with alumina particles

An integrated adhesive wear model was proposed by the author in the previous studies whereby an exponential equation was used to model the transient wear; and the Archard's wear equation to model the steady-state wear. Wear coefficient equations were successfully formulated by using the transient wear data obtained from pin-on-disc wear tests performed with aluminium-based matrix composites reinforced with different volume fraction of alumina (Al 2O 3) particles. A methodology was developed to predict the net steady-state wear coefficient with a suitable F A value. In this study, this methodology was extended to predict the standard steady-state wear coefficient. It was found that with a F A value of 0.99, the predicted wear coefficient values had an average deviation of about 17% as compared with experimental data obtained previously. Furthermore, this methodology was found capable of predicting the required sliding distance as well. It thus has the potential to save time and resources to obtain more accurate results in wear testing. F A is an exponential function defined in this paper.

Prediction of Net Steady-State Wear Coefficient in an Al-Al2O3(P)/Steel System with an Integrated Wear Model

Experimental pin-on-disc wear tests were carried out previously on three types of commercial A6061 aluminum-based matrix composites (MMCs) reinforced with 10, 15 and 20% alumina particles, respectively, against steel disc, with both the moving-pin technique developed at Nanyang Technological University and the conventional pin-on-disc technique. An integrated wear model was established, with the transient wear volume described by an exponential equation while the steady-state wear by a revised Archard equation. A wear coefficient equation was formulated by using the transient wear data to model the standard wear coefficients of both the transient wear and the steady-state wear successfully. In this study, a new equation was developed from the previous model to predict the net steady-state wear coefficient. With a F A value of 0.999 or 0.9999, the average deviation from the measured values was about 26%. F A was an exponential function used in the transient wear equation. On the other hand, Peterson's equation was also found suitable for modeling the steady-state wear of the three types of aluminium-based matrix composites. However it lacked some of the features the newly proposed equation could provide.

Prediction of Steady-State Wear Coefficients in Adhesive Wear

With an integrated adhesive wear model, Yang's second wear coefficient equation was previously found suitable for modeling the standard wear coefficients for both the transient wear and the steady-state wear of MMC-A, MMC-B, and MMC-C, which are aluminium-based matrix composites containing 10%, 15%, and 20% alumina particles, respectively. In this study, Yang's third wear coefficient equation was used to predict the standard wear coefficient and the net steady-state wear coefficient, respectively, for MMC-D, an aluminium alloy matrix composite containing 20% spherical alumina particles, and an aluminium alloy A6061-T6. As compared with the wear data obtained previously, the average deviations were found to be about 23% and 15%, respectively, for the predicted standard wear coefficients and about 20% and 65% for the predicted net steady-state wear coefficients for the two materials respectively. The high deviation of about 65% obtained for the aluminium alloy was due to the very low wear rate obtained during wear testing with a long sliding distance, with the presence of powdery debris.

Synthesis of an Al-ZrO2 composite by infiltration of Zr-chelates into an Al matrix

Aluminium-based matrix composites were prepared by infiltration with an ammoniacal zirconium chelate within an Al matrix synthesized via Aluminium powder compactation. After infiltration, this chelate can be transformed in situ by sol-gel method that leads to tetragonal phases in zirconia, which in turn, transforms to monoclinic structure on heating. Based on Differential Thermal Analysis (DTA), Fourier Transformed Infrared (FTIR), X-Ray Diffraction (XRD), and Scanning Electron Microscopy (SEM), we confirm the reaction sequence to obtain the tetramer, the phase transformation sequence within the Al matrix, and the development of phases that leads to the synthesis of the Al-ZrO2 composite.

Wear coefficient equation for aluminium-based matrix composites against steel disc

A new formulation of the wear coefficient was developed and tested experimentally. Two different types of pin-on-disc wear tests were conducted using three commercial, A6061 aluminum-based metal–matrix composites (MMCs). One type of test resulted in a spiral track and the other a circular track. Hardened tool steel discs were used as the sliding counterface for MMC pins having 10, 15 and 20% alumina reinforcements. A new wear equation was derived and shown to be a better predictor of steady-state wear coefficients. It is based on an exponential transient wear volume equation and Archard’s equation.

Microstructural and mechanical characteristics of in situ metal matrix composites

During the past decade, considerable research effort has been directed towards the development of in situ metal matrix composites (MMCs), in which the reinforcements are formed in situ by exothermal reactions between elements or between elements and compounds. Using this approach, MMCs with a wide range of matrix materials (including aluminum, titanium, copper, nickel and iron), and second-phase particles (including borides, carbides, nitrides, oxides and their mixtures) have been produced. Because of the formation of ultrafine and stable ceramic reinforcements, the in situ MMCs are found to exhibit excellent mechanical properties. In this review article, current development on the fabrication, microstructure and mechanical properties of the composites reinforced with in situ ceramic phases will be addressed. Particular attention is paid to the mechanisms responsible for the formation of in situ reinforcements, and for creep failure of the aluminum-based matrix composites.

Effect of cutting fluid on the machinability of metal matrix composites

This paper utilizes models for cumulative tool wear to study the effect of cutting fluid on the machinability of aluminum-based matrix composites reinforced with SiC or Al 2O 3 particles. Pressurized cutting fluid neither improves nor worsens the tool life because of either effective flushing of the chips or lack of a lubricating film. The surface finish and the cutting forces are insensitive to cutting fluid and cutting speed when machining with a new diamond tool, but deteriorate with greater tool wear.

Shock-compacted aluminum/boron carbide composites

The aim of this study was to verify that explosive consolidation can be used as a processing route to produce metal-matrix composites, comprising an aluminum-based matrix and boron-carbide reinforcement. Composites containing 30, 50 and 70 volume percent boron carbide in an MB 85 aluminum-alloy matrix were successfully compacted at 10–12 GPa pressure. Transmission electron microscopy was used to examine the resulting microsctructure and interface quality. It is predicted that the high density of dislocations produced during the compaction will lead to accelerated aging in age-hardenable aluminum alloy matrices.

Discontinuous reinforcements in extruded aluminium-lithium matrix composites

Aluminium-based matrix composites with ceramic reinforcements have received considerable attention because of their improved strength, modulus and increased wear resistance over conventional aluminium alloys. The discontinuous type of reinforcements, in this case SiC and Si 3N 4 particulates, have been especially appealing due to their relative availability and low-cost production. In addition, adding lithium to aluminium alloys has the potential for even better properties with weight reductions, highly attractive for the aerospace industries. This paper discusses both the role of discontinuous reinforcements and extrusion parameters in the development of these improved metal-matrix composites (MMCs). The effects of different reinforcements, varying percentages of reinforcements and the relative sizes of these reinforcements were studied with respect to the microstructural development and the consequent mechanical properties.

A New Approach to the Study of the GP (I) Zone Stability in AlCu Alloy by Means of Extended Hiickel Molecular Orbital Calculations

Extended Huckel molecular orbital (EHMO) calculation was applied to study the stability of a solute cluster, the so-called Guinier-Preston (GP) (I) zone, that appears at a low ageing temperature in AlCu alloys. To investigate the reason that the solute cluster is preferentially formed in {001} planes of supersaturated aluminium-base matrix, the stabilities of hypothetical solute clusters lying in three different crystallographic planes indexed with (001), (110), and (111) were compared, based on the total energy which is calculated quantum-mechanically for an individual model-cluster. The internal structure of GP (I) zones in AlCu alloys were also investigated. Lastly influences of additional elements on the stability of the GP (I) were examined with the EHMO calculation.

Composition and lattice parameters of a new aluminium-rich borocarbide

High-strength and low-weight composite materials or cermets have been prepared by reinforcing an aluminium-base matrix with boron carbide particles or with boron carbide-coated boron fibres [1-3]. In the former case boron carbide (B4C) is the strengthening agent, whereas in the latter the role of B4C coating is to protect the fibres against a too severe attack by aluminium during processing or use of the composites. Recently B4C-coated carbon fibres have been produced on a pilot plant in our laboratory [4, 5]. A general study is now in progress with the aim of employing these treated fibres for the manufacture of aluminium-base matrix composites. The development of such materials and improvement of their performances require, however, a thorough understanding of the metal-carbide interface chemistry and, primarily, a detailed description of the phases likely to be formed by chemical reaction in the A1-B-C system. In a general study on the processing of B4C-A1 cermets, Halverson et al. observed the formation of a new ternary compound, which they called phase X, at every temperature between 800 and 1400 °C [1]. Attempts were made by Sarikaya et al. [6] to characterize that phase by electron diffraction and energy-loss spectroscopy: those authors proposed a hexagonal symmetry with the lattice parameters a 0 = 0.3520 nm and Co = 0.5820 nm and the chemical formula A14BC. This letter reports the composition and lattice parameters of an aluminium-rich borocarbide that was prepared by direct synthesis from the elements and discusses the possible relationship between this compound and the foregoing phase X. Commercial powders of aluminium (purity 99.8 wt %, grain size d < 50 txm, Alfa Ventron), boron (99.4 wt %, d < 250/xm, Alfa Ventron) and carbon (spectrographic grade, d < 25/xm, Le Carbone Lorraine) were ball-mixed in a steel mortar at the atomic ratio AI:B :C = 80:10:10 and cold-pressed under 272 MPa into small rods (dimensions 4 m m x 6 m m x 3 0 m m and weight about 2g). These rods were placed on an alumina boat and heated for 160 h at 1273 K in a closed silica tube under atmospheric-pressure purified argon. Under these conditions the weight losses were <5%. After air-cooling the resultant samples were characterized by X-ray powder diffraction (XRD), using standard Philips equipment: a PW1720 generator, PW1390 channel-control unit and PW1050/25 two-circle goniometer supplied with a step-scanning motor

Microstructure and mechanical properties of Al-Al2O3-MgO cast particulate composites

Al-Al2O3-MgO cast particle composites prepared by an MgO coating technique were investigated for their microstructural and mechanical property features. In all, sixteen compositions of the composite were subjected to this study. Generally, a uniform distribution of Al2O3 particles was observed in the composites. But in the upper half portion of the cylindrical castings, Al2O3 particles were found to segregate along the grain boundaries and also within the grain-forming chain-like structures. The microhardness of the base matrix revealed that the retention of submicrometre MgO particles causes dispersion strengthening. In the case of maximum strengthening, the microhardness of the base matrix rises to 35 kg mm−2 from 19 kg mm−2 for as-cast pure aluminium. The composites also displayed excellent high-temperature tensile properties up to 250°C (523 K). At the level of 21%V f retention of Al2O3, the composite displayed a UTS value of 110 MN m−2 with corresponding 0.2% offset yield strength of 65 MN m−2 and 12% elongation at ambient temperature. At 150° C (423 K) and 250° C (523 K), the composite retains 69% and 53%, respectively, of its room-temperature UTS value. This was the optimum retention of Al2O3 and the best composite obtained in the present work. The excellent high-temperature characteristics of the composite are thought to be due to the sum total effect of both the submicrometre MgO particles and the coarser Al2O3 particles retained in the aluminium base matrix.

Microstructure and superconducting properties of melt-quenched insoluble Al-Pb and Al-Pb-Bi alloys

In order to obtain aluminium-based superconducting alloys including finely dispersed lead or Pb-Bi particles, the application of the melt-quenching technique has been tried for Al-Pb, Al-Si-Pb and Al-Si-Pb-Bi alloys containing immiscible elements such as lead and bismuth. It has been found to result in the preparation of superconducting materials consisting of fcc Pb or h c p e(Pb-Bi) particles dispersed finely and densely in the aluminium-based matrix in each composition range below about 2 at % Pb for Al-Pb alloys and 5 at % Pb or (Pb + Bi) for (Al0.9 Si0.1)100−x Pbx and (Al0.9Si0.1)100−x (Pb0.6Bi0.4)x alloys. The particle size and interparticle distance were ∼ 40 nm and 40 to 100 nm, respectively, within the grains, and ∼ 100 nm and below ∼ 30 nm, respectively, at the grain boundaries for the lead phase in Al98 Pb2 alloy. Particle size was ∼ 15 to 60 nm and interpartide distance 30 to 60 nm for the Pb- Bi phase in (Al0.9 Si0.1)95(Pb0.6 Bi0.4)5 Transition temperature,Tc was 4.16 K for Al98Pb2, 3.94K for (Al0.9Si0.1)95 Pb5 and 7.75 K for (Al0.9Si0.1)95(Pb0.6Bi0.4)5. The upper critical magnetic field,Hc2, and critical current density,Jc, for (Al0.9Si0.1)95(Pb0.6Bi0.4)5 were 0.22 T at 4.2 K and 1.67 × 107 Am−2atzeroappliedheld and 4.2 K. The appearance of the superconductivity for the aluminium -based alloys was interpreted as due to the formation of superconducting percolation path along the tangled dislocations, sub-boundaries and/or grain boundaries where Pb and Pb-Bi phases precipitated preferentially.