Aluminum Matrix Research Articles

The Evolution of Grain Microstructure in Friction Stir Welding of Dissimilar Al/Mg Alloys with Ultrasonic Assistance.

The process of grain refinement during welding significantly influences both the final microstructure and performance of the weld joint. In the present work, merits of acoustic addition in the conventional Frictions Stir Welding (FSW) process were evaluated for joining dissimilar Al/Mg alloys. To capture the near "in situ" structure around the exit hole, an "emergency stop" followed by rapid cooling using liquid nitrogen was employed. Electron Backscatter Diffraction analysis was utilized to characterize and examine the evolution of grain microstructure within the aluminum matrix as the material flowed around the exit hole. The findings reveal that two mechanisms, continuous dynamic recrystallization (CDRX) and geometric dynamic recrystallization (GDRX), jointly or alternatively influence the grain evolution process. In conventional FSW, CDRX initially governs grain evolution, transitioning to GDRX as material deformation strain and temperature increase. Subsequently, as material deposition commences, CDRX reasserts dominance. Conversely, in acoustic addition, ultrasonic vibration accelerates GDRX, promoting its predominance by enhancing material flow and dislocation movements. Even during the material deposition, GDRX remains the dominant mechanism.

Bifunctional nano-SiO2 additive for reinforcing the SiC/Al composites fabricated via a novel hybrid additive manufacturing

In this work, a novel hybrid additive manufacturing technique is used to prepare the SiC/Al composites. The effect of silica sol concentration on the microstructure and property of SiC preforms and SiC/Al composites were investigated. Silica sol infiltration proved to be an efficient strategy to address the troublesome issue of strength decrease for the SiC preforms after preoxidation. With an increase in silica sol concentration from 0 to 30 %, the strength of the pre-oxidised SiC preforms increased from 0 to 2.77 ± 0.21 MPa, which well satisfied the processing requirements of the subsequent vacuum-pressure infiltration process. Interestingly, the nano-SiO2 in the silica sol not only is favorable for the SiC–Al interface of SiC/Al composite, but also has a significant grain refinement effect on the aluminium matrix. As a result, the strength of the samples treated with preoxidation and silica sol infiltration reached a maximum value of 411.41 MPa, which was 88.38 % higher than 218.4 MPa of the control group. Meanwhile, a notable enhancement in fracture strain was observed from 0.125 to 0.156 % for the optimized SiC/Al composite. More importantly, the large-size and high-performance SiC/Al composite parts with complex structures have been successfully prepared by this hybrid additive manufacturing technique. The results of this work show that the hybrid additive manufacturing technology has great potential for application in aerospace, automotive industry and other fields.

Microstructural evolution and mechanical properties of aluminum-graphite composites processed via accumulative roll bonding

In the present work, the aluminum-graphite metal matrix composites were fabricated via accumulative roll bonding (ARB). The graphite powder particles of <50 μm were introduced into aluminum in three different weight percentages. The effect of graphite on the evolution of microstructure, interface formation, and mechanical properties was studied. The microstructural investigation revealed that the amount of graphite played a vital role. A better particle distribution was observed for 1.25 and 1.5 wt%. However, a further increase in the reinforcement to 2.2 wt% shows longer flaky graphite with comparatively sharing a larger interface area with the matrix aluminum. An FE-SEM/EDS (Field Emission-Scanning electron microscopy/Energy dispersive Spectroscopy) line mapping at the aluminum-graphite interface confirmed an intact sound interface with better adherence properties. The ultimate tensile strength of the composites drastically improved with an increasing number of ARB passes. The FE-SEM taken over the fractured surface of the composite revealed that the ARBed Al-1100 and the composites failed in ductile mode. It was observed that the graphite particle was the primary source of nucleation in the composites. The voids have nucleated at the particle-matrix interface, followed by their growth and coalescence.

Enhancing mechanical properties of aluminium 6063 with crab shell particle reinforcement

The versatility and beneficial properties of aluminium 6063 make it an excellent material for various applications, but limited in engineering production where strength is a major material selection factor. The utilization of natural resources in material science has gained prominence due to the quest for sustainable and innovative materials. This work explores the development and characterization of an aluminium matrix composite reinforced with crab shell particles (CSPs). The CSPs are produced via the milling process for 72 h and the CSPs are incorporated in varying percentages (0–20 wt%) into the aluminium matrix using a stir casting technique, the mechanical properties (tensile strength, compressive strength, % elongation, and impact energy) of the composites are determined using an Instron universal testing machine (UTM) and a Charpy impact testing machine, respectively. A scanning electron microscope (SEM) is used to examine the microstructure of the composite fracture surfaces and Gywddion 2.65 software is used to view the SEM images of the fracture surfaces in three dimensions (3D). The results revealed that tensile strength, compressive strength, % elongation, and impact energy are enhanced by adding varying percentages of CSPs on the aluminium 6063 composites.

Atomic strain concentration induced by interfaces in extruded carbon nanotube reinforced 2024Al matrix composite

Inhomogeneous deformation occurs in aluminum matrix composite, resulting in strain concentration near reinforcement/matrix interfaces. In this work, for the CNT/2024Al composite extruded by porthole die extrusion, the effects of reinforcements (CNTs and Al4C3) and intermetallic (Al2Cu) on atomic strain concentration and grain boundary migration were systematically studied. The results indicate that obvious atomic strain concentration appears near the CNT/Al and Al4C3/Al interfaces, and then, the strain is transferred from the interfaces to Al matrix. Mirco-Al2Cu phases are mainly distributed at grain boundaries, increasing Zener force, and thus inhibit grain growth of the composite. In addition, the Al4C3/Al and Al2Cu/Al interfaces are observed, and the (111)Al atom plane is parallel to 1̄107Al4C3, while large number of misfit dislocations are observed near the Al2Cu/Al interface. Transmission Kikuchi diffraction and transmission electron microscope observations indicate that the grains, which contains more second phases, exhibit higher dislocation density than neighboring grains, providing driving force for grain boundary migration. High extrusion temperature brings about Al2Cu dissolution, leading to grain growth, and interfacial bonding strength decreases with increasing extrusion speed. Consequently, the composite extruded at low-temperature and low-ram speed has ultrafine grains, high dislocation density, and strong interfacial bonding, exhibiting high hardness, tensile strength and elongation.

Investigation of the mechanical properties of TiC particle-reinforced Al–Cu alloys: Insights into interface precipitation mechanisms and strengthening effects

The increase in the mechanical performance of Al–Cu alloys through TiC particle reinforcement represents a significant improvement in the field of aluminum alloy strengthening. However, the precipitation behavior at the aluminum matrix and TiC interface requires further exploration. In this study, the induced precipitation mechanisms at the TiC interface and the impact of interface precipitates on bonding were investigated through scanning transmission electron microscopy (STEM) and first-principles calculations. The results indicate that θ′-Al2Cu exhibits heterogeneous nucleation on the TiC substrate, and the (100) Al/(110) θ′-Al2Cu/(100) TiC interface structure possesses the lowest formation energy. Consequently, the precipitation of θ′-Al2Cu at the Al/TiC interface demonstrates thermodynamic preference and energy stability. Tensile simulations reveal that the presence of interface precipitates effectively enhances the strength of the interface structure. Electronic structure analysis indicates a “barrel effect” in the stretched interface model, with fracture occurring in the weakest-bonded Al lattice near the phase interface. Additionally, θ′-Al2Cu, acting as an interface adhesive, enhances the chemical bond strength between Al and TiC interface atoms. This work provides novel insights into particle-induced interface precipitation behavior and interface fracture mechanisms.

Study on the valorisation of laminated waste as radon barriers for indoor spaces

Nowadays, there is a severe problem with waste generation, especially with single-use packaging. Although the trend is to try to recycle or reuse this waste, a significant amount still ends up in landfills, which represents a serious environmental problem. This waste includes laminated materials, which are difficult to recycle because the polymeric material and aluminium layers cannot be separated easily. This work proposes the study of the valorisation of several laminated wastes as radon barriers for indoor spaces due to the similarity in composition between these waste and commercial radon barriers. For this purpose, the diffusion coefficient of laminated wastes composed of polymeric and aluminium materials, with thicknesses between 70 and 500 μm, has been calculated using a modification of the ISO/TS 11665–13:2017 standard. The diffusion coefficients obtained are in the range of 10−12 and 10−14 m2/s, a reduction of radon concentration of over 90%, and a high radon resistance is achieved in all cases. These results show the excellent capacity of these materials to slow down radon and indicate that these wastes could be reused to manufacture radon barriers giving a new life to these materials and contributing to sustainable development and a circular economy.

Shear response and deformation mechanism of boron nitride nanosheets reinforced aluminum matrix composites

Atomistic simulations are performed to study the shear response and deformation mechanism of boron nitride nanosheet (BNNS) reinforced aluminum (Al) matrix composites. In this work, stacked BNNS/Al composites and dispersed BNNS/Al composites with various BNNS layers are constructed, respectively. Our computations show that the wrinkle deformation of BNNS under shear loading does not lead to the loss of load-bearing capacity. However, the yield of the Al matrix causes it to lose load-bearing capacity. The occurrence of wrinkles in BNNS aggravates the plastic failure of the Al matrix. High BNNS volume fraction increases the shear modulus and flow stress of stacked BNNS/Al composites but decreases the shear strength. Compared with stacked BNNS/Al composites, the mechanical properties of dispersed BNNS/Al composites are remarkably improved with the increase of BNNS interface in both elastic and plastic stages. In addition, the BNNS interface is able to obstruct the propagation of dislocations and stacking faults in the Al matrix. These findings may deepen our understanding of the mechanical properties and deformation mechanisms of BNNS/Al composites.

Investigation on the micro-cutting mechanism of aluminum matrix composites with ultrasound elliptical vibration

Investigation on the micro-cutting mechanism of aluminum matrix composites with ultrasound elliptical vibration

A review on processing, mechanical and wear properties of Al matrix composites reinforced with Al2O3, SiC, B4C and MgO by powder metallurgy method

This study focused on improving the mechanical strength and wear resistance of aluminum matrix composites (AMCs) produced by powder metallurgy, which are critical in industrial applications. In this review study, studies involving the preparation and characterization of aluminum based composite materials reinforced with Al2O3, SiC, B4C and MgO powders using the powder metallurgy method have been comprehensively evaluated. Literature shows that changes in sintering time, temperature, and composition of powders can affect critical properties such as material density, hardness, and wear resistance. In general, the increase in sintering time and sintering temperature generally increased the density and reduced the amount of porosity of composite materials consisting of aluminum-based Al2O3, SiC, B4C and MgO powders. Increasing the compaction pressure generally increased the material density and created a more homogeneous structure. When the properties of each material were examined, it was determined that SiC and B4C provide higher strength, hardness and wear resistance, and therefore can be preferred especially in high-performance applications such as automotive, aerospace, defense industry and cutting tools.

Simultaneously increasing the mechanical properties and corrosion resistance of B4C/Al composites via forming “TiO2–Al” interfacial layer

In this work, we use a simple and efficient method to introduce “TiO2–Al” interfacial layers between the B4C particles and aluminium (Al) matrix in TiO2@B4C/Al composites by combining the ball milling dispersion process with the pressure infiltration technology. It is anticipated that it would improve the mechanical properties and corrosion resistance. The work demonstrates that the coefficient of thermal expansion (CTE) of the “TiO2–Al” interfacial layer is between those of the matrix and the reinforcement. Thus, it relieves the residual stresses in the composites. Furthermore, the low residual stress of the composites achieved by introducing the “TiO2–Al” interfacial layer results in delayed failure and the low corrosion tendency. The composites containing “TiO2–Al” interfacial layers show remarkable bending properties (a strength of 668.6 MPa) and good corrosion resistance (a low corrosion current density of 6.81 μA cm−2). Thus, the TiO2@B4C/Al composites exhibit remarkable mechanical properties and corrosion resistance compared with the composites reported in the literature.

Efficient and stable dehydrogenation of methylcyclohexane over Pt supported on mesoporous alumina with excellent textural properties

Mesoporous alumina (MA) materials with outstanding textural properties have been synthesized by a facile approach, and were evaluated as supports of Pt-based catalyst for methylcyclohexane dehydrogenation. At 300 °C, the resultant catalyst demonstrates a much higher activity with a maximum hydrogen evolution rate of 2081 mmol/gPt/min in comparison with the state-of-the-art alumina supported Pt catalysts. Interestingly, even after a long-time reaction of 100 h or regeneration, more than 80% of original activity was still maintained. The superior catalytic performance of the obtained catalyst is associated with the high specific surface area and large mesoporous size of support MA, thus benefiting the increase in the number of Pt active sites and efficiently inhibiting the formation of coke deposition during the reaction. Our contribution has provided a rational design strategy for highly efficient and stable dehydrogenation catalysts, which is a key for the utilization of methylcyclohexane-toluene system in hydrogen storage technology.

Spatial and temporal dynamics of thermal motion of a chain of liquid lead nanoinclusions attached to a fixed dislocation segment in an aluminum matrix

Thermal motion of a chain of liquid lead nanoinclusions attached to a dislocation segment fixed at its ends in the aluminum-based alloy was studied in situ using TEM in the temperature range from 442 °C to 497 °C. The projections of points of the trajectories of the inclusions onto the dislocation line were analyzed. The evidence for the collective interaction of all the inclusions and their spatially correlated collective thermal motion was obtained. Also, moderate temporal autocorrelation of thermal motion of the inclusions and a very weak temporal cross-correlation of thermal motion of the inclusions in all pairs was shown. The FFT phase spectra of the time dependencies of the inclusions positions on the dislocation segment give the evidence for the phase synchronization of thermal oscillations of the inclusions. It is shown that the thermal oscillations of the terminal inclusion attached to the dislocation node and elevation of temperature lead to decrease in the level of synchronization of thermal oscillations of the inclusions in the chain. It is indicated that the development of the process of desynchronization of thermal oscillations of the inclusions manifests itself by an increase in the density of phase steps in the initially linear unwrapped phase spectra accompanying by an increase in the interaction of the steps.

Microstructure and properties of ZrB2-reinforced aluminum matrix composites consolidated by ECAP process

In this research work, the effects of mechanical alloying and subsequent compaction by ECAP on the microstructural, physical, and mechanical properties of Al-ZrB2 metal matrix composites (MMCs) were evaluated. To prepare composite powders, a mixture of Al and ZrB2 particles was mechanically alloyed at various times of 1, 6, 12, 18 and 24 h. SEM micrographs indicate that the size of the obtained particles decreases by increasing the time of mechanical alloying up to 18 h. However, after this time, increasing the time of mechanical alloying has led to an increase in the size of the particles. By means of mechanical alloying for 18 h, the average size of fine particles reached 823 nm, while coarse particles were 8 μm. The calculation via the use of XRD examination implies that the mean crystallite size of powder decreased from about 68 nm to 31 nm and 26.8 nm, for Al and Al-5%ZrB2 samples, respectively, while lattice strain increased from 0.25% to 0.64% and from 0.3% to 0.73% after 1 h to 24 h milling of same samples, respectively. However, the rate of crystallite size reduction after 12 h of mechanical alloying is gradually reduced, and that is reached its lowest level after 18 h. After that, increasing the time of mechanical alloying has led to a saturation in the lattice strain. In continue, the resulting composite powder was heated, consolidated and turned into bulk material by warm equal channel angular pressing (ECAP) at the temperature of 250 °C. The resultant optimum composite has been characterized by EDS elemental mapping. Microhardness measurements and shear punch tests were performed to evaluate the mechanical properties of the unreinforced and composite samples after the ECAP process. The Al-ZrB2 MMC bulk samples subjected to ECAP, with a ZrB2 amount of 5 wt%, had a relative density, hardness, and ultimate shear strength of 99.3%, 170 HV, and 151 MPa, respectively, using powders which have been mechanically alloyed up to 24 h.

Mechanical properties and bonding mechanism on interfaces containing work-hardening surface layer of roll-bonded 6061 Al/Q235 steel composite plates

The film theory is widely accepted as a bonding mechanism of metallic laminate composites (MLCs). It states that the fresh metal contact after the rupture of the surface film is an important condition for the bonding of MLCs. However, the bonding performance and mechanisms at the interfaces containing surface films have not been sufficiently investigated. In this study, steel–aluminium composite plates were used to study the bonding state, elemental diffusion behaviour, and mechanical properties of the bonding interface between the steel-side work-hardened surface layer (WHSL) and the aluminium matrix. The results indicate that the Al and Mg atoms inside the Al matrix can diffuse to about 100–150 nm into the WHSL (Fe3O4) and undergo selective oxidation, thus generating Fe0.1MgAl2O4 particles during annealing. However, the Fe atoms in the WHSL cannot diffuse into the aluminium matrix, thereby preventing the WHSL–Al interface from generating intermetallic compounds and maintaining beneficial bonding properties after long-term annealing. Additionally, compared to the steel–aluminium composite plate without a WHSL, the steel–aluminium composite plate with a WHSL exhibited a superior bonding performance. It also demonstrated an elongation increase of 28.67%, the mechanism of this increased elongation was also studied. Under the same degree of bending, the composite plates with WHSL maintained a stable bonding state and formed a unique interface deformation mode around the WHSL–Al interface after bending, which are highly desirable bending properties.

Variation in wear scar penetration depths due to impact angle on the erosion wear of advanced aluminum matrix nanocomposites

In present study, developing (Al-Fe-Si) materials with high wear and erosion resistance for aerospace components, such as wing skin and fuselage sections, presents a significant challenge for researchers. This study delves into the reinforcement effects of TiC in aluminum composites, produced via ultrasonic-assisted stir casting. The focus lies on exploring the UASC technique to create composites with varied TiC weight percentages (0 %, 2 %, 4 %, and 6 % by weight) and evaluating their erosion resistance. Experiments varied erodent particle impact angle, velocity, and discharge rate, alongside impingement angles, and maintaining a constant velocity of 151 m/s for 10-minute durations, using solid particles averaging 201 µm in size. Increasing TiC content improved erosion resistance. Optical profilometry revealed a −131 µm maximum wear scar depth at a 45° impingement angle, with significantly higher erosion wear compared to other angles. These findings offer valuable insights for enhancing mechanical system design and durability. Eroded surface failure analysis utilized FE-SEM images to examine composites impacted by erodent forces.

Strong and tough 3D-(SiC–Si3N4)/Al co-continuous composite with enhanced interfaces

Materials with high specific strength and toughness are urgently needed in the fields of electronic packaging, armor, and aerospace. SiC/Al composites show good potential for these applications but the problem of mutual exclusion of strength and toughness still needs to be solved. Herein, we propose a new strategy to simultaneously enhance its strength and toughness from the perspective of structural optimization and interface enhancement. Inspired by the nacre structure, a 3D-(SiC–Si3N4)/Al co-continuous composite was prepared by freeze-casting combined with the pressure infiltration method. During the process, elongated Si3N4 grains were introduced into the ceramic framework to design the internal lamella wall structure and increase the contact area with the aluminum substrate. Moreover, a favorable interfacial bonding was designed between Si3N4 and Al to improve interface wettability. The reliable microstructure of porous 3D-(SiC–Si3N4) preform was tailored through the adjustment of initial solid loading and the α-Si3N4 component. The effects of initial solid loading and the α-Si3N4 component on the microstructure, interfacial wettability, and mechanical properties of the final composites were investigated. The results showed that the SiC–Si3N4/Al composites possess high flexural strength (769 MPa) and fracture toughness (15.1 MPa m1/2), which is superior to data reported in general literature. Numerous elongated β-Si3N4 grains are produced on the ceramic skeleton, forming an interlocking structure with the aluminum matrix, which increases the contact area with the aluminum substrate. A chemical reaction layer was formed at the interface of the composite, greatly improving the interfacial bonding strength. This work provides a promising design guideline for developing and optimizing high-strength and tough composite.

Advancements in Aluminum Matrix Composites: A Comprehensive Review on the Mechanical and Microstructural Attributes of Rare Earth Elements (REEs) and Rare Earth Oxides (REOs) Doped Materials

Advancements in Aluminum Matrix Composites: A Comprehensive Review on the Mechanical and Microstructural Attributes of Rare Earth Elements (REEs) and Rare Earth Oxides (REOs) Doped Materials

Wave propagation in context of Moore–Gibson–Thompson thermoelasticity with Klein–Gordon nonlocality

Understanding plane and surface waves in elastic materials is crucial in various fields, including geophysics, seismology, and materials science, as they provide valuable information about the properties of the materials they travel through and can help in earthquake detection and analysis. In the present paper, the governing equations of Moore–Gibson–Thompson (MGT) thermoelasticity are modified in context of Klein–Gordon (KG) nonlocality. For linear, homogeneous and isotropic case, the governing equations in two-dimensions are solved to obtain the dispersion relations for possible plane waves. It is found that there exists one transverse and two coupled longitudinal waves in a two-dimensional model of MGT weakly nonlocal thermoelastic medium and the speeds of these plane waves are found to be dependent on KG nonlocal parameters. The coupled longitudinal waves are also found to be dependent on conductivity rate parameter. For linear, homogeneous and isotropic case, the governing equations in two-dimensions are also solved to obtain a Rayleigh wave secular equation at thermally insulated surface. For a numerical example of aluminium material, the speeds of transverse wave, coupled longitudinal waves and the Rayleigh wave are computed and graphically illustrated to visualize the effects of KG nonlocality parameters, conductivity rate parameter and the angular frequency on the wave speeds.

Multi-Objective Optimization of Novel Aluminum Welding Fillers Reinforced with Niobium Diboride Nanoparticles

New and innovative technologies have expanded the quality and applications of aluminum welding in the maritime, aerospace, and automotive industries. One such technology is the addition of nanoparticles to aluminum matrices, resulting in improved strength, operating temperature, and stiffness. Furthermore, researchers continue to assess pertinent factors that improve the microstructure and mechanical characteristics of aluminum welding by enabling the optimization of the manufacturing process. Hence, this research explores alternatives, namely cost-effective aluminum welding fillers reinforced with niobium diboride nanoparticles. The goal has been to improve weld quality by employing multi-objective optimization, attained through a central composite design with a response surface model. The model considered three factors: the amount (weight percent) of nanoparticles, melt stirring speed, and melt stirring time. Filler hardness and porosity percentage served as response variables. The optimal parameters for manufacturing this novel filler for the processing conditions studied are 2% nanoparticles present in a melt stirred at 750 rpm for 35.2 s. The resulting filler possessed a 687.4 MPA Brinell hardness and low porosity, i.e., 3.9%. Overall, the results prove that the proposed experimental design successfully identified the optimal processing factors for manufacturing novel nanoparticle-reinforced fillers with improved mechanical properties for potential innovative applications across diverse industries.