Al Alloy Matrix Research Articles

Fabrication process and bending properties of carbon fibers reinforced Al-alloy matrix composites

Woven carbon fibers reinforced Al–Mg (95–5wt%) matrix composites were successfully prepared by an electromagnetic casting method. In order to improve the wetting behavior, different stabilizers were respectively used in the electroless plating process to coat the fibers with a better Ni/P layer. The lactic acid offered the most outstanding stabilizing effect. The casting results indicated that the contact time between the molten metal and the carbon fibers was vital to the bonding degree: increasing the solidification time significantly reduced the cavity defects which located near the interface; however, an overly long solidification time would result in a tendency to crack in the centers of the woven fibers. The hot-pressing treatment with optimum parameters significantly mitigated the crack and cavity defects which are common in the composite prepared through casting method. The appropriate applied compression ratio turned out to be approximately 6%. Three point bending test showed that the bending strength of the composite had an improvement for 33.6% than that of Al-alloy matrix.

Mechanical Properties of 7075 Aluminium Matrix Composites Reinforced by Nanometric Silicon Carbide Particulates

Aluminum Matrix composites (AMCs) are known as light weight and high-strength materials with their potential application in areas such as aerospace, automobile, defence, engineering and other industries. AMCs have the advantage to significantly reduce the overall weight of the vehicles and aircraft while maintaining their structural strength. Reinforcement of micron or nano-sized range particles with aluminium matrix yields improved mechanical and physical properties in composite materials. The strength of Al matrix composites will be improved about 20% with decreasing reinforcement particle size from micrometric scale to nanometric scale. In this study, Al7075 alloy and nano SiC composites have been fabricated by Electromagnetic stir casting process combined with mechanical stirring. Different weight % of nano SiC particles (0.5, 1, 1.5, and 2 wt%) were used for synthesis of composites. Certain test methods scanning electron microscopy (SEM) and X-Ray diffraction (XRD) are used to examine the microstructure along with the measurement of impact strength of the nano composite. SEM microstructure shows SiC particles are fairly infused into the matrix alloy with agglomeration and porosity at some places. X-Ray Diffraction (XRD) analysis acknowledged that no unknown crystalline elements are present in the composites while mixing reinforcement with Al alloy matrix. The results impact strength shows that impact strength decreases with respect to the base metal because of brittle nature of reinforcement.

Mechanical and Morphological Studies of Al6061-Gr-SiC Hybrid Metal Matrix Composites

Abstract. In recent years, Aluminium alloy based metal matrix composites (MMC) are gaining wide spread acceptance in several aerospace and automobile applications. These composites possess excellent wear resistance in addition to other superior mechanical properties such as strength, modulus and hardness when compared with conventional alloys. The hybrid composites are new generation of composites containing more than one type, shape or sizes of reinforcements giving superior combined properties of reinforcements and the matrix. In the present work, Al6061 has been used as matrix material and the reinforcing materials selected were SiC and Graphite particulates of 10 to 30µm size. Composites Al6061-Gr (2- 8 wt. %), Al6061-SiC (2 -10wt. %) and Hybrid composites with Al6061 matrix alloy containing 3wt% graphite and varying composition of 2-10wt% SiCp were prepared by stir casting technique. The cast matrix alloy and its composites have been subjected to solutionizing treatment at a temperature of 530 ± 20C for 6 hours, followed by ageing at a temperature of 175 ± 20C for 6 hours. The mechanical properties of as cast and T6 heat treated composites have been evaluated as per ASTM standards and compared. Addition of Graphite particulates into the Al6061 matrix improved the strength and ductility of the composites. Significant improvement in tensile strength and hardness was noticed as the wt. % of SiCp increases in Al6061-SiC composites. Addition of Graphite into Al6061-SiC further improved the strength and ductility of hybrid composites. The heat treatment process had the profound effect in improving the mechanical properties of the studied composites. The microstructural studies revealed the uniform distribution of SiC and Gr particles in the matrix system.

Effect of the interfacial reaction of aluminum and yttrium oxide on aging behavior of aluminum–magnesium–silicon alloy reinforced with yttrium oxide modified sub-micron alumina

Age-strengthening behavior of Al–Mg–Si alloy composites reinforced with sub-micron alumina particles modified by yttrium oxide under the temperature of 130°C, 160°C and 190°C was investigated. The mechanical performances of unmodified and modified composites after the aging treatment were evaluated with the tensile test. The results indicate that the hardness level of modified composites is obviously increased compared to unmodified composites at different aging states, and the process of aging precipitation of the matrix alloy in modified composites is accelerated by the interfacial reaction of aluminum and yttrium oxide. The aging microstructures of modified composites have a significant difference compared to non-modified composites, and present a large amount of dislocations and precipitates in the matrix alloy. The modified composites treated by the aging exhibit excellent tensile properties. It is suggested that the interfacial reaction resulted from the surface modification of particles with the rare-earth yttrium oxide is beneficial in promoting the process of aging precipitates and strengthening the aging microstructures and properties of Al alloy matrix in modified composites.

Development of Novel Al-Alloy (Al-5Mg)/10Wt.%TiB<sub>2</sub> Metal Matrix Composites by <i>In Situ</i> Reaction Synthesis

The present paper describes a cost effective route to produce Al alloy-10 wt % TiB2 metal matrix composites by in-situ molten flux assisted reaction synthesis. Now a days main focus is given to aluminium alloy as a matrix material due to its unique combination of good corrosion resistance, low density, superior mechanical properties, good vibration damping, higher wear resistance due to which alloy finds extensive applications in naval applications. With TiB2 as particulate addition in Al-Alloy (Al-5Mg) matrix properties of alloy can greatly be improved.

Effects of ball milling and particle size on microstructure and properties 5083 Al–Ni composites fabricated by friction stir processing

Ni particles were incorporated in a 5083 Al alloy matrix by friction stir processing (FSP) to fabricate metal particle reinforced composite. During the optimization of the process parameters for uniform particle distribution, it was found that ball-milled finer particles (10μm) were dispersed more uniformly in the matrix compared to as-received coarse particles (70μm). Hence, the particles were ball-milled before incorporating into 5083 Al matrix. The finer ball-milled particles were dispersed uniformly, however a thin intermetallic layer was formed at the particle-matrix interface. The layer was found to be Al–Ni intermetallic. When as-received fine particles of similar size (10μm) were incorporated using the same FSP parameters no such layer was observed in the processed composite. Hence, ball milling of particles influenced the microstructure of the composite. The high-energy state of the ball-milled particles can be attributed to the formation of the interfacial layer. The strength of both the composite was higher compared to the unreinforced 5083 Al alloy. FSP also refined the grain size of the aluminum matrix from 25µm to 3.5µm and this also contributed to the strength enhancement of the composites. The strength and ductility of the ball-milled composite were lower as expected compared to the composite with as-received fine Ni particles due to the presence of the interfacial reaction layer.

Microstructure and mechanical properties of z-pinned carbon fiber reinforced aluminum alloy composites

Abstract We report that metal z-pin can be used to enhance the interlaminar strength of carbon fiber reinforced aluminum alloy (Cf/Al) composites. The Cf/Al composites incorporated with AISI 321 steel z-pins as interlaminar reinforcement were fabricated by pressure infiltration, resulting in high composite density. The steel pin reacted with the Al alloy matrix and formed a continuous interfacial reaction layer of FeAl3 to provide strong interfacial bonding between the steel pin and Al alloy matrix. Moreover, it has been found that the diameter of the z-pin has a significant influence on the thickness of the interfacial reaction layer. Double-notched interlaminar shear testing showed that the z-pins increased the shear strength of the Cf/Al composite by 70%–230%.

Metal/ceramic Interface Structures and Segregation Behavior in Aluminum-based Composites

Abstract Trimodal Al alloy (AA) matrix composites consisting of ultrafine-grained (UFG) and coarse-grained (CG) Al phases and micron-sized B4C ceramic reinforcement particles exhibit combinations of strength and ductility that render them useful for potential applications in the aerospace, defense and automotive industries. Tailoring of microstructures with specific mechanical properties requires a detailed understanding of interfacial structures to enable strong interface bonding between ceramic reinforcement and metal matrix, and thereby allow for effective load transfer. Trimodal AA metal matrix composites typically show three characteristics that are noteworthy: nanocrystalline grains in the vicinity of the B4C reinforcement particles; Mg segregation at AA/B4C interfaces; and the presence of amorphous interfacial layers separating nanocrystalline grains from B4C particles. Interestingly, however, fundamental information related to the mechanisms responsible for these characteristics as well as information on local compositions and phases are absent in the current literature. In this study, we use high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, electron energy-loss spectroscopy, and precession assisted electron diffraction to gain fundamental insight into the mechanisms that affect the characteristics of AA/B4C interfaces. Specifically, we determined interfacial structures, local composition and spatial distribution of the interfacial constituents. Near atomic resolution characterization revealed amorphous multilayers and a nanocrystalline region between Al phase and B4C reinforcement particles. The amorphous layers consist of nonstoichiometric AlxOy, while the nanocrystalline region is comprised of MgO nanograins. The experimental results are discussed in terms of the possible underlying mechanisms at AA/B4C interfaces.

Properties of High Volume Fraction Fly Ash/Al Alloy Composites Produced by Infiltration Process

In the present study, pressure infiltration is employed to synthesize aluminum alloy 7075-fly ash composites. The microstructure and chemical composition of the fly ash and the produced composite material was examined using optical and scanning electron microscopy, as well as x-ray diffraction. Several properties of the produced composite material were examined and evaluated including macro-hardness, wear, thermal expansion, and corrosion behavior. The wear characteristics of the composite, in the as-cast conditions, were studied by dry sliding wear tests. The corrosion behavior of composite material was evaluated by means of potentiodynamic corrosion experiments in a 3.5 wt.% NaCl solution. The composite specimens exhibit a homogeneous distribution of fly ash particles and present enhanced hardness values, compared to the matrix material. The high volume fraction of the fly ash reinforcement (>40%) in the composite material led to increased wear rates, attributed to the fragmentation of the fly ash particles. However, the presence of fly ash particles in the Al alloy matrix considerably decreased the coefficiency of thermal expansion, while resulting in an altered corrosion mechanism of the composite material with respect to the matrix alloy.

Effect of Pass Deformation on the Microstructure and Properties of Aluminum Alloy Anodes for Fuel Cell Application

he effect of pass deformation on the microstructure of Al-Mg-Sn-Bi-Ga-In alloy anode was investigated by using SEM, TEM, and EBSD. The results show that when controlling the rolling deformation at 40%, the segregation phases on the Al alloy matrix was the best distributed for the reason of dynamic recrystallization procedure. The electrochemical and anti-corrosion results show that uniform distribution of segregation phase will improve the related properties of Al alloy anode. After optimizing the rolling procedure, the Al alloy anode has more negative electrode potential of about -1.585V(vs.Hg/HgO) and lower hydrogen evolution rate of 0.092mL/ (min·cm2)

Effect of electroceramic particles on damping behaviour of aluminium hybrid composites produced by ultrasonic cavitation and mechanical stirring

Abstract In this study, electroceramics PBN and PLZT along with SiC were included in Al–3.96 wt.% Mg (A514.0) master alloy. Ultrasonic cavitation (UST) and mechanical stirring (MS) were employed to improve wettability and dispersion during casting. Two composite systems were produced: PBN system (5 wt.% PBN + 1 wt.% SiC and 15 wt.% PBN + 1 wt.% SiC) and the PLZT system (follows the same designation). The influence of fabrication method on the microstructures, particle distribution and wettability as well as electroceramic impact on dynamo-mechanical properties of prepared composites were investigated. Optical microscope (OM) and scanning electron microscope (SEM) results indicate that the processing technique was effective as it promoted wettability and homogeneous dispersion of particles throughout the Al matrix. Dynamic mechanical analysis (DMA) study of the composites demonstrated that the addition of the functional particles to the Al alloy matrix improved damping capacity ( Tan δ ) at 200 °C. The composites exhibited an increase in Tan δ of 24.3 ± 0.3% and 91.4 ± 0.2% for 5 and 15 wt.% PBN + 1 wt.% SiC and an increase of 19.7 ± 0.5% and 42.5 ± 0.3% for 5 and 15 wt.% PLZT + 1 wt.% SiC, respectively, when compared to the aluminium alloy matrix.

Application of ball milling in the synthesis of AA 7075–ZrO2 metal matrix nanocomposite

Ball milling was used to reduce the particle size of yttria-stabilized ZrO2 powders with the aim of introducing it into the AA 7075 matrix. It was observed that during the mechanical milling of the ZrO2 powders a destabilization of the tetragonal structure occurred, which was confirmed by the X-ray diffraction results. A transition from tetragonal to monoclinic structure resulted as a consequence of the application of ball milling. The synthesis of the composite was carried out in the same way by applying mechanical ball milling in order to disperse 2 and 5wt.% of zirconium oxide particles into the Al alloy matrix. It was found that longer times were needed for the 5wt.% of ZrO2 to achieve a complete dispersion into the matrix, unlike 2wt.% of ZrO2 sample, being 15 and 10h, respectively. It was evident that the presence of ZrO2 particles had a marked influence upon the powder morphology and particle size of the matrix during the milling process. Despite the structural change observed, a relatively good homogenous dispersion of ZrO2 particles was found after ball milling.

Mechanical Performance of Carbon Nanotube-Reinforced Nanocomposites

There is a continuous demand for next-generation industrial materials because they offer advantages such as high performance, reliable life cycle, reasonable cost, and ease of mass production. Carbon nanotubes (CNTs), which possess unique properties such as beneficial mechanical, electrical, and thermal properties, as well as chemical stability, have received considerable attention as candidates for reinforcing ultra-high-performance nanocomposites. CNT-reinforced Al alloy matrix nanocomposites were fabricated by mechanical ball-milling and hot-pressing processes. The effects of different CNTs on the mechanical properties of the composites were investigated. The mechanical properties were found to change significantly depending on the type of CNT blended with the matrices. The mechanical performance of the nanocomposites can thus be controlled by using different types of CNT reinforcements.

Metal/ceramic interface structures and segregation behavior in aluminum-based composites

Trimodal Al alloy (AA) matrix composites consisting of ultrafine-grained (UFG) and coarse-grained (CG) Al phases and micron-sized B4C ceramic reinforcement particles exhibit combinations of strength and ductility that render them useful for potential applications in the aerospace, defense and automotive industries. Tailoring of microstructures with specific mechanical properties requires a detailed understanding of interfacial structures to enable strong interface bonding between ceramic reinforcement and metal matrix, and thereby allow for effective load transfer. Trimodal AA metal matrix composites typically show three characteristics that are noteworthy: nanocrystalline grains in the vicinity of the B4C reinforcement particles; Mg segregation at AA/B4C interfaces; and the presence of amorphous interfacial layers separating nanocrystalline grains from B4C particles. Interestingly, however, fundamental information related to the mechanisms responsible for these characteristics as well as information on local compositions and phases are absent in the current literature. In this study, we use high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, electron energy-loss spectroscopy, and precession assisted electron diffraction to gain fundamental insight into the mechanisms that affect the characteristics of AA/B4C interfaces. Specifically, we determined interfacial structures, local composition and spatial distribution of the interfacial constituents. Near atomic resolution characterization revealed amorphous multilayers and a nanocrystalline region between Al phase and B4C reinforcement particles. The amorphous layers consist of nonstoichiometric AlxOy, while the nanocrystalline region is comprised of MgO nanograins. The experimental results are discussed in terms of the possible underlying mechanisms at AA/B4C interfaces.

Microstructure and Mechanical Properties of Mg–7.4% Al Alloy Matrix Composites Reinforced by Nanocrystalline Al–Ca Intermetallic Particles

Mg–7.6% Al (in mass fraction) alloy matrix composites reinforced with different volume fractions of nanocrystalline Al3Ca8 particles were synthesized by powder metallurgy, and the effect of the volume fraction of reinforcement on the mechanical properties was studied. Room temperature compression test reveals considerable improvement on mechanical properties as compared to unreinforced matrix. The compressive strength increases from 683 MPa for unreinforced alloy matrix to about 767 and 823 MPa for the samples having 20 and 40 vol% of reinforcement, respectively, while retaining appreciable plastic deformation ranging between 12 and 24%. The specific strength of the composites increased significantly, demonstrating the effectiveness of the low-density Al3Ca8 reinforcement.

Nanoquasicrystalline Al-based matrix/γ-Al2O3 nanocomposites

Quasicrystalline aluminium alloys have been studied in the past years achieving higher strength than commercial Al alloys and retaining high strength at high temperature. In this work a quasicrystalline Al alloy matrix nanocomposite containing nanoceramic particles has been manufactured using ball milling and hot extrusion. For that purpose a nanoquasicrystalline Al–Fe–Cr–Ti alloy was manufactured by powder atomisation. Nanocomposites consisting of a quasicrystalline Al–Fe–Cr–Ti alloy matrix and reinforcement of γ-Al2O3 nano particles were manufactured. The effect of ball milling time on the microstructure and microhardness of the nanocomposite powders was investigated. Bulk materials were produced by consolidation and hot extrusion. The microstructure and microhardness of the extruded materials were characterised.The milling regime behaviour is discussed, and shows three different steps that have a significant effect on the rate of change of uniformity of the reinforcement distribution, matrix microstructure, powder size distribution and its microhardness. No significant decomposition of the quasicrystalline phase occurred over 30h of milling. Strain increased and the crystallite size of the aluminium phase decreased with milling time, with the Al crystallite size reaching a steady state. Although the quasicrystalline phase decomposed during hot extrusion, the microhardness of the nanocomposite produced is significantly harder (227±3μHV500) than both the unreinforced quasicrystalline alloy (159±1μHV500) and crystalline aluminium nanocomposites reported in the literature [1]. Methods and analysis of material behaviour put forward in this work inform further understanding and optimisation of this and other nanocomposite systems containing a metastable microstructure matrix.

Microstructural characterization and mechanical property of Fly Ash/Al-25Mg composites

Fly ash/A1-Mg composites are fabricated by powder metallurgical method. The morphology and structure of fly ash/A1-Mg composites are characterized by scanning electron microscope (SEM) and X-ray diffraction, respectively. The influences of different fly ash content on the friction and wear behavior of the composites are investigated at a constant sliding velocity of 400 r/min and the worn mechanism of composites is discussed. The results indicate that the friction coefficient is steadily lower than that of Al alloy matrix at the lower fly ash content and loads. For the fly ash/A1-Mg composites, the wear mechanism is characterized as abrasive wear and adhesive wear under small normal load and at low fly ash content, and it is characterized as delamination wear and abrasive wear transferred onto the counterpart under high normal load and at high fly ash content.

Microstructural characteristics and mechanical properties of carbon nanotube reinforced aluminum alloy composites produced by ball milling

The influence of milling time on the structure, morphology and thermal stability of multi-walled carbon nanotubes (MWCNTs) reinforced EN AW6082 aluminum alloy powders has been studied. After structural and microstructural characterization of the mechanically milled powders micro- and nano-hardness of the composite powder particles were evaluated. The morphological and X-ray diffraction studies on the milled powders revealed that the carbon nanotubes (CNTs) were uniformly distributed and embedded within the aluminum matrix. No reaction products were detected even after long milling up to 50h. Nanotubes became shorter in length as they fractured under the impact and shearing action during the milling process. A high hardness of about 436±52HV is achieved for the milled powders, due to the addition of MWCNTs, after milling for 50h. The increased elastic modulus and nanohardness can be attributed to the finer grain size evolved during high energy ball milling and to the uniform distribution of hard CNTs in the Al-alloy matrix. The hardness values of the composite as well as the matrix alloy compares well with that predicted by the Hall–Petch relationship.

Dry Sliding Wear Behavior of Graphite Particulate Reinforced Al6061 Alloy Composite Materials

This present paper is an investigation made to study the un-lubricated sliding wear behavior of Al6061 alloy composites reinforced with graphite particulates of size 100-125 μm. The content of graphite in the alloy was varied from 6-9% in steps of 3 wt. %. The liquid metallurgy technique was used to fabricate the composites. A pin-on-disc wear testing machine was used to evaluate the volumetric wear loss, in which a hardened EN32 steel disc was used as the counter face. The results indicated that the volumetric wear loss of the composites was lesser than that of the Al6061 matrix alloy and it further decreased with the increase in graphite content up-to 6 wt.%. For composites containing 9 wt. % of graphite particulates, the volumetric wear loss was more than that of 6wt. % composites, but lesser than base matrix alloy. However, the material loss in terms of wear volume increased with the increase in load and sliding speed, both in case of composites and the alloy.

In situ formed Al3Ti particles in Al alloy matrix and their effects on the microstructure and mechanical properties of 7075 alloy

Abstract