Particle Reinforced Aluminum Matrix Composites Research Articles

Analysis and Optimization of the Machining Characteristics of High-Volume Content SiCp/Al Composite in Wire Electrical Discharge Machining

With the properties of high specific strength, small thermal expansion and good abrasive resistance, the particle-reinforced aluminum matrix composite is widely used in the fields of aerospace, automobile and electronic communications, etc. However, the cutting performance of the particle-reinforced aluminum matrix composite is very poor due to severe tool wear and low machining efficiency. Wire electrical discharge machining has been proven to be a good machining method for conductive material with any hardness. Even so, the high-volume SiCp/Al content composite is still a difficult-to-machine material in wire electrical discharge machining due to the influence of insulative the SiC particle. The goal of this paper is to analyze the machining characteristics and find the optimal process parameters for the high-volume content (65 vol.%) SiCp/Al composite in wire electrical discharge machining. Experimental results show that the material removal method of the SiCp/Al composite includes sublimating, decomposing and particle shedding. The material removal rate is found to increase with the increasing pulse-on time, first increasing and then decreasing with the increasing pulse-off time, servo voltage, wire feed and wire tension. Pulse-on time and servo voltage are the dominant factors for surface roughness. In addition, the multi-objective optimization method of the nondominated neighbor immune algorithm is presented to optimize the process parameters for a fast material removal rate and low surface roughness. The optimized process parameters can increase the material removal rate by 34% and reduce the surface roughness by 6%. Furthermore, the effectiveness of the Pareto optimal solution is proven by the verified experiment.

Microstructures, mechanical properties, and aging behavior of hybrid-sized TiB2 particulate-reinforced 2219 aluminum matrix composites

Particulate-reinforced aluminum matrix composites are widely used owing to their advantageous comprehensive performance. For these composites, aging treatment is an important and essential process. However, researchers have discrepant opinions regarding the exact effects of particles on the aging behavior. In this study, the aging behavior of TiB2/2219Al composites is analyzed in terms of thermodynamics and kinetics. The results reveal that the particles can both promote aging and impede aging, and the peak aging times of the composites are advanced in this study. The effects of hybrid-sized TiB2 particles on the microstructures and mechanical properties of aged TiB2/2219Al composites are investigated. The results show noticeable dislocation propagation after the addition of TiB2, and this is confirmed by transmission electron microscopy observations and modified Williamson–Hall equation calculations. The Vickers hardness values are increased under all aging conditions. The strengths of the naturally aged composite, yield strength of the under-aged composite, and Young's modulus are increased significantly, whereas the strengths of composites under other aging conditions record only slight improvement. The total elongations of all the composites are decreased owing to the presence of TiB2 agglomerates.

Effect of stress concentration and deformation temperature on the tensile property and damage behavior of a B4Cp/Al composite

In the present work, the influence of stress concentration and deformation temperature on the mechanical behavior of boron carbide particles reinforced aluminum matrix (B4Cp/Al) composites fabricated by powder metallurgy was investigated via the tensile test and finite element simulation based on the real microstructure. The results demonstrate that a uniform particle distribution and a good interface bonding between the particles and matrix are found in the 5 wt% B4Cp/6061Al composite. When the deformation temperature decreases from 298 to 77 K, the tensile property and notch sensitivity ratio of the notched composite increases. Combined with the microstructure observation and stress/strain evolution, the fracture mechanism of the notched composite at 77 K was revealed. Specifically, there is a difference in stress and strain distributions induced by deformation temperature in the initial stage of deformation of the notched composite. The matrix damage tends to occur from the notch and propagate to the high strain regions near the particles. Furthermore, there is a high possibility of particle fracture or interface debonding in the notched composite due to the high matrix stress at 77 K. This work provides the experimental and theoretical basis for the application of particle-reinforced aluminum matrix composites with stress concentration under cryogenic environments.

Effect of ball milling time on the structural characteristics and mechanical properties of nano-sized Y2O3 particle reinforced aluminum matrix composites produced by powder metallurgy route

Mechanical milling presents an effective solution in producing a homogenous structure for composites. The present study focused on the production of 0.5 wt% yttria nanoparticle reinforced 7075 aluminum alloy composite in order to examine the effects of yttria dispersion and interfacial bonding by ball milling technique. The 7075 aluminum alloy powders and yttria were mechanically alloyed with different milling times. The milled composites powders were then consolidated with the help of hot pressing. Hardness, density, and tensile tests were carried out for characterizing the mechanical properties of the composite. The milled powder and the microstructural evolution of the composites were analyzed utilizing scanning and transmission electron microscopy. A striking enhancement of 164% and 90% in hardness and ultimate tensile strength, respectively, were found compared with the reference 7075 aluminum alloy fabricated with the same producing history. The origins of the observed increase in hardness and strength were discussed within the strengthening mechanisms' framework.

Superplastic behavior of an in-situ TiB2 particle reinforced aluminum matrix composite processed by elliptical cross-section torsion extrusion

In this work, a severe plastic deformation method, namely elliptical cross-section torsion extrusion ( E -TE), was applied to achieve superplasticity of an in-situ TiB 2 /Al-Zn-Mg-Cu composite by obtaining the optimized microstructure of uniformly distributed particles and equiaxed-fine grains. The superplastic behavior and mechanisms of the E -TE processed composite were comprehensively investigated via tensile tests (at T = 350 °C–500 °C and ε ̇ = 10 −1 s −1 -10 −3 s −1 ) and microstructure characterizations. The tests demonstrated that the composite after a single pass of the E -TE gained a maximum elongation of 420% at 450 °C × 10 −3 s −1 . Even with the strain rate increasing to 10 −2 s −1 , the elongation still reached 360%, which implies a high strain rate superplasticity. Analysis based on the strain rate sensitivity ( m ≈ 0.20–0.35) and microstructure characterizations showed that the deformation and failure mechanisms of the composite vary with the temperature. When the temperature is within 350 °C–400 °C, the composite realizes deformation mainly through intragranular dislocation slip and fails by intragranular fracture. With the temperature of 425 °C–450 °C, the deformation is attributed to cooperative grain boundary sliding (CGBS) accommodated by dislocation activity and liquid phase, where a small fraction of liquid phases observed at the triple junctions of GBs facilitates the composite's superplasticity by reducing the stress concentration and deformation incompatibility. The failure is ascribed to the intergranular fracture by cavity formation/coalescence. For temperature within 475 °C–500 °C, numerous liquid phases formed at GBs and significantly weakened the GBs' strength, deteriorating the composite's superplasticity. The composite's failure is resulted from the intergranular fracture by strength weakening of GBs. • Particle reinforced aluminum matrix composites after elliptical cross-section torsion extrusion (E-TE) show superplasticity. • The E-TE processed composite exhibits an elongation of 360% at 450℃×10 -2 s -1 , implying a high strain rate superplasticity. • The superplastic deformation/failure mechanisms of the E-TE processed composite vary with temperatures. • The composite's superplasticity is facilitated by the appropriate liquid phase at the optimized temperature of 450℃.

Synthesis of nano- to micrometer-sized B4C particle-reinforced aluminum matrix composites via powder metallurgy and subsequent heat treatment

Synthesis of nano- to micrometer-sized B4C particle-reinforced aluminum matrix composites via powder metallurgy and subsequent heat treatment

Preparation of in-situ AlN-TiC nanoparticles and their refinement and reinforcement effects on Al-Zn-Mn-Cu alloy

Compared with the particle reinforced aluminum matrix composites (PRAMCs) with single-phase reinforcing particles, hybrid aluminum matrix composites (HAMCs) have attracted many researchers in the world due to the well performance in industrial production and application, which achieved gratifying results. In this work, in-situ AlN and TiC nanoparticles were produced by high-energy ball milling. To improve the wettability with the aluminum matrix, AlN-TiC/Al composite ribbons were prepared by melt spun. Then, the ribbons were added to the Al-Zn-Mn-Cu alloy to prepare AlN-TiC/Al-Zn-Mn-Cu composite. Meanwhile, the ultrasonic vibration was used to ameliorate the distribution of AlN and TiC nanoparticles in the matrix. The results shown that AlN and TiC nanoparticles had a significant effect on the refinement and reinforcement of the composite. The ultimate tensile strength of the composite had a 10.6% increase, while the increase on the elongation is 20.0%. The excellent mechanical properties were mainly due to the dual-phase enhancement of in-situ AlN and TiC with two sizes of nanoparticles as well as the well-bonded interface between them and the matrix. Moreover, the improvement on the mechanical properties of the composite can benefit from the multiple strengthening mechanisms, including fine grain strengthening, coefficient of thermal expansion (CTE) mismatch strengthening and Orowan strengthening. The microstructure, orientation relationship, mechanical properties and strengthening mechanisms of the AlN-TiC/Al-Zn-Mn-Cu composite were investigated.

Numerical Analysis of Particulate Migration Behavior within Molten Pool during TIG-Assisted Droplet Deposition Manufacturing of SiC Particle-Reinforced Aluminum Matrix Composites.

A transient three-dimensional (3D) numerical model was established to illustrate the heat transfer, fluid flow and particle migration behaviors in the molten pool during TIG-assisted droplet deposition manufacturing (DDM) of SiC particle-reinforced aluminum matrix composites (AMCs). The effect of temperature-dependent physical properties and the interaction between the SiC reinforcement and the liquid metal matrix were considered. A double-ellipsoidal volumetric heat source model was adopted to simulate the energy interactions between the pulse square-wave variable polarity TIG welding arc and the moving substrate. Free surface fluctuations of molten pool due to arc force and sequential droplet impact are calculated with volume of fluid (VOF) method in a fixed Eulerian structured mesh. The numerical model, capable of capturing the impact, simultaneous spread, and phase change of the droplets as well as the motion trajectory and terminate distribution state of the reinforcement particles, is key tool to understand the formation mechanism of the TIG-assisted DDM of SiC particle-reinforced AMCs. The numerical model was validated by the metallographic observations, and the calculated particle distribution and solidification morphology of deposited layer agree well with the experimental measurements.

Microstructural, Mechanical and Tribological Characterization of Friction Stir Welded A7075/ZrB2 In Situ Composites

Friction stir welding (FSW) has emerged as an efficient technique for the welding of aluminum alloys. However, its potential for the welding of particulate reinforced aluminum matrix composites (AMCs) is yet to be explored fully. The reinforcements affect welding process because it complicates microstructural modifications in weld zone, mainly in nugget zone (NZ). Thus, the present study was aimed to investigate the effect of FSW process on microstructural features and assess the quality of weld after welding of A7075/ZrB2 in situ composites. The microstructural features were captured through optical microscopy, scanning electron microscopy and electron back-scattered diffraction technique. The results revealed, after friction stir welding, that ZrB2 clusters broke completely and dispersed uniformly in the NZ. It was also observed that aluminum matrix experienced substantial grain size reduction due to dynamic recrystallization caused by frictional heat and plastic deformation. The joint efficiency of the welded structure was judged by tensile test. The obtained result revealed a higher value (≥ 90%) which may be ascribed to grain size reduction, uniform dispersion of ZrB2 particles and increased particle/matrix interface characteristics along with eradication of casting defects. The improved microstructural features led to higher hardness and wear resistance in NZ of friction stir welded composite. Spalling and delamination were predominant wear mechanisms in the welded and un-welded as-cast A7075 alloys, whereas these mechanisms were not significant in welded as well as un-welded A7075/ZrB2 in situ composites.

Fabrication and characterization of in-situ Al3Ni intermetallic and CeO2 particulate-reinforced aluminum matrix composites

Al-xNi-yCeO2 (x = 6, 10, 15, 20 and y = 0, 5, 10 wt%) composites were produced by a powder metallurgical production route. Powder mixtures of Al, Ni and CeO2 were fabricated via mechanical alloying (MA) for 4 h in a Spex-type high-energy ball mill. Both the mechanically alloyed (MAed) and non-MAed (as-blended mixtures) powders were pre-compacted in a hydraulic press under 650 MPa and then pressurelessly consolidated at 630 °C for 2 h under an inert atmosphere. The effects of MA process and the amounts of Ni and CeO2 on the microstructural, mechanical and tribological properties of the sintered composites were determined. Based on the SEM and XRD investigations, the MAed powders illustrated a homogenous structure, comprising flaky particles with smaller crystallite sizes and greater lattice strain. According to the XRD analysis, Ni formed Al–Ni intermetallic compounds in the matrix of sintered composites that act as secondary reinforcement phases. The SEM observations conducted on the MAed samples demonstrated more uniformly and finely distributed Al3Ni and CeO2 phases in the microstructure of the MAed samples, unlike the non-MAed ones. The hardness values of sintered composites increased due to the MA process and increasing Ni and CeO2 amounts, and the hardness value of the MAed Al20Ni–10CeO2 sample reached 179 HV. The ultimate compressive strength and failure strain of the MAed Al6Ni–10CeO2 sample were 441 MPa and 11.3%. In the Al20Ni–10CeO2 sample, the compressive strength and failure strain were 391 MPa and 5.5%, respectively. Additionally, the reciprocating wear test results illustrated that both wear resistance and hardness values of the composites increased as the amounts of Ni and CeO2 increased, and the Al20Ni–10CeO2 sample exhibited the highest wear resistance as 0.175 × 10-3 mm3/Nm.

Study on effects of tool nose radius on the formation mechanism of edge defects during milling SiCp/Al composites

Silicon carbide particulate reinforced aluminum matrix composites (SiCp/Al) have received considerable attention in many engineering applications. However, the existence of dispersing SiC particles leads to particularly vulnerable edge quality of SiCp/Al composites in machining. It is very significant to improve the edge defects of SiCp/Al composites by optimizing the tool geometry. Cutting tool nose radius mainly determines the machining performance. Therefore, the effects of tool nose radius on the chip topography, cutting force, and edge geometry in face and dry milling of 20% SiCp/Al composites were investigated in the current work. Experiments were conducted with tool nose radius of 0.5, 1, 1.5, and 2 mm. The results showed that the shorter and wider chips were found with the increment in tool nose radius. It was also observed that the cutting force increased with the increment in tool nose radius. Based on the material removal mechanism with different tool nose radius, the feature maps of edge defects in SiCp/Al composites were established and studied. It was found that the outer and inner edge quality of the materials was improved with the increase of tool nose radius.

Numerical Simulation and Experimental Study on Compound Casting of Layered Aluminum Matrix Composite Brake Drum.

The requirements of high-strength, wear-resistance and lightweight of brake drums have been continually increasing in recent years and any specific aluminum alloy or particle-reinforced aluminum matrix composites may not satisfy all the demands. Combining dissimilar materials to play their respective advantages is a solution to this problem. In this study, a compound casting method was used to combine solid SiCp/A357 composite and a liquid 7050 aluminum alloy to prepare an aluminum matrix composite with a layered structure. The ProCAST numerical simulation software was used to predict the heat transfer in compound casting process and guide the preheating temperature of the wear-resistant ring in the experiment. An Optical Microscope (OM) and Scanning Electron Microscope (SEM) were used to observe microstructures around the solid–liquid bonding interface, the element distribution and phase component of which were analyzed by Energy Dispersive Spectroscopy (EDS) and mechanical properties were evaluated by microhardness and shear tests. The results showed that the interface of the layered aluminum matrix composite prepared by this method achieved complete metallurgical bonding and a transition zone formed on the solid surface. After T6 heat treatment, the average shear strength of the interface increased from 19.8 MPa to 33.8 MPa.

Study of Nanoscale Wear of SiC/Al Nanocomposites Using Molecular Dynamics Simulations

In this work, molecular dynamics simulations are performed to investigate the nanoscale wear behavior of SiC particle-reinforced aluminum matrix composites (SiC/Al NCs) through nanoscratching using a spherical diamond indenter. A series of simulations are conducted to explore the effects of scratching depth, scratching speed, temperature, indenter size, and particle size during the nanoscratching process. We find the dislocation strengthening in the nanoscratching of SiC/Al NCs. It is also found that the frictional force and normal force increase with the increase of scratching depth, indenter size, and nanoparticle size. Moreover, the friction coefficient increases with the scratching depth. However, the friction coefficient declines with the increase of indenter size and nanoparticle size. Furthermore, for a larger scratching speed, the frictional force becomes smaller, while the normal force becomes larger, which is mainly determined by the competition between strain rate hardening and thermal softening. We also find that both the frictional force and normal force become smaller for a higher temperature resulting from thermal softening effect. The insights into the nanoscale wear properties of SiC/Al NCs lay a foundation for the wide applications of SiC/Al NCs.

Microstructure and mechanical properties of novel high-entropy alloy particle reinforced aluminum matrix composites fabricated by selective laser melting

An Al matrix composite reinforced with high-entropy alloy (HEA) particles was successfully fabricated by selective laser melting (SLM). The composite fabricated with optimized parameters exhibits a high strength (901 ± 13 MPa) due to the presence of HEA phases and high dislocation density.

Effects of ultrasonic rolling on the surface integrity of in-situ TiB2/2024Al composite

Mechanical surface modification is of great significance to the final engineering applications of particles reinforced aluminum matrix composites (PRAMCs) as structural materials. In the present study, in-situ 6 wt% TiB2/2024Al composite was surface-modified by ultrasonic rolling (UR). The surface integrity of the modified composite was comprehensively analyzed and assessed in terms of surface morphology, topography, microstructure, residual stress (RS), strain hardening (SH), and microhardness. Results showed that a single pass of UR treatment with a set of preselected parameters can directly improve the surface finish of the fine-turned samples by 1.5 orders of magnitude. The grain structure in the superficial layer can be effectively refined. High-level and profound compressive residual stress (RSc) and SH were introduced into the sample surface, which can be beneficial for the composite to resist multiple modes of mechanical failures. Besides, a sophisticated finite element (FE) simulation was conducted, which described the UR process fairly well from a numerical viewpoint. It is worth noting that the newly observed discretization mechanism of TiB2 clusters indicates the feasibility of modifying the surface distribution of the reinforcements, which brings about a brand-new and low-cost way to enhance the surface comprehensive mechanical properties of PRAMCs.

Microstructural evolution and mechanical behavior of powder metallurgy based SiC/Al–Mg-Sc-Zr nanocomposite subjected to multi-pass friction stir processing

Abstract Powder metallurgy (PM) is a versatile technique to fabricate the particulate reinforced aluminum matrix composites (AMCs) by combining Al alloy powders with various types of reinforcement particles. However, the AMCs fabricated by PM generally lack ductility due to processing-related factors such as porosity, oxygen content, and undesirable microstructural features initiated by the contamination during powder preparation or sintering. In this study, the 5 wt% SiC/Al–Mg-Sc-Zr nanocomposite produced by PM was subjected to friction stir processing (FSP) to obtain the dense, uniform and refined microstructures and the attendant improved mechanical properties. The effect of FSP passes on the microstructural features and mechanical properties of as-PM nanocomposite was investigated, and the strengthening and toughening mechanism of FSPed nanocomposite was revealed. The results showed that the FSP passes with the opposite moving direction of FSP tool between the consecutive passes, largely affected the microstructure of the stir zone. Increasing FSP passes significantly reduced the microdefects and homogenized the microstructure. After 4-pass FSP, the whole stir zone consisting of the dense, uniform and refined microstructure, was obtained. This resulted in an increase in yield strength from 92 MPa in the as-PM condition to 161 MPa after 4-pass FSP, and a simultaneous nearly double enhancement in fracture strain from 0.11 to 0.29.

Effects of process parameters on jet electrochemical machining of SiC particle-reinforced aluminum matrix composites

Silicon carbide particle-reinforced aluminum matrix composites (SiCp/Al) are increasingly applied in high-end industries because of their excellent comprehensive material properties. However, as a typical difficult-to-cut material, machining of SiCp/Al using traditional processes faces serious challenges. Jet electrochemical machining (Jet-ECM) is a new-generation electrochemical machining (ECM) technology, which exhibits improved process flexibility and machining accuracy, in addition to the basic advantages of the ECM process. Jet-ECM appears to be a potential alternative machining technology for SiCp/Al to achieve high machining rate and damage-free surface. In the present work, the polarization curves obtained by electrochemistry study showed that a passivation-tanspassivation transition behavior with increasing the voltage occurs in NaNO3 electrolyte, while NaCl electrolyte causes active behavior. Thus, compared to NaCl electrolytes, the NaNO3 electrolyte is relatively suitable for Jet-ECM of SiCp/Al because of its potential to improve the machining localization. Besides, the effects of process parameters (including voltage, electrolyte type, and concentration) on the machining performance were systematically investigated. It was found that the voltage has the most significant influence on the machined dimple profile. A higher voltage helps in achieving a large depth. The surface roughness is dependent on the selection of the electrolyte and voltage. The NaNO3 electrolyte is preferred to realize smooth surface. Additionally, it was found that with increasing voltage, the surface roughness increases. Finally, this work was extended to be Jet-ECM with linear movement of the nozzle, and well-formed SiCp/Al grooves can be obtained using the selected process parameters.

Comparison of mechanical and wearing properties between LM6, LM6/B4C and LM6/B4C/Gr aluminium metal matrix composites

Due to greater specific modulus, better wear resistance, excellent specific strength, and declined coefficient of thermal expansion value, particulate reinforced aluminum matrix composites have acquired appreciable consideration. Casting route and powder metallurgy are the commonly used fabrication methods from which we select stir casting technique due to its simplicity and low expense. In this study mechanical properties like tensile strength, yield strength, hardness, wear, coefficient of friction (COF) and frictional properties of light metal (LM6), LM6/ Boron Carbide (B4C) and LM6/B4C/Graphite (Gr) 2% were analyzed with the aid of Universal Testing Machine (UTM), Rockwell Hardness Tester and Pin on Disk Tester. B4C was chosen due to its excellent reinforcement properties compared to silicon carbide (SiC) and alumina. Gr (2%)was added in one sample to obtain better tribological as well as better sliding lubricating characteristics. The test outcomes reveal that by increasing the percent of B4C particles in theLM6 matrix, the mechanical as well as tribological properties are improved and the new material developed can replace conventional LM6 aluminium alloy in its applications.

Microstructure, mechanical and wear behaviour of Al7075/SiC aluminium matrix composite fabricated by stir casting

Application of particulate reinforced composite is being emphasized day by day due to its modified strength, high hardness, less weight, and ductility. This paper deals with the behaviour of physical, mechanical and tribological properties of aluminium matrix composite reinforced by micro-sized silicon carbide particles (in a various quantity such as 0, 3, 6 and 9 wt.%) prepared by stir casting fabrication process. With the increase in weight percentage of SiC reinforcement, the density of composite improves from 2.76 gm/cc to 2.83 gm/cc, and the porosity of composite reduces from 1.78% to 0.56%. UTS and Hardness of SiC particle reinforced aluminium matrix composites developed from 140 MPa to 205 MPa and 66 HV to 84 HV respectively. Microstructure reveals that strong bonding develops between matrix and reinforcement in terms of strength and hardness in all the formed composites compared to its matrix material. Comparatively less wear is observed with enhancing SiC content conducted by the pin on disc dry sliding wear test for all the formed composites.

Microstructural characteristics and mechanical behavior of microwave-assisted sintered ferromagnetic FeCoNi1.5CrCu HEAp/Al matrix composites

The preparation of metal particle reinforced aluminum matrix composites by powder metallurgy has been widely studied in recent years. In this work, the effect of microwave sintering temperature on the microstructure and mechanical behavior of high-entropy alloys (HEAs) reinforced aluminum matrix composites prepared by powder metallurgy was investigated. Due to the outstanding microwave absorbing property of ferromagnetic HEAs particles, the composites sintering proceeded efficiently. At 480 °C, the aluminum matrix in the composite material is more compact, and the HEAs particles in the composite material are more evenly distributed, and the interface between HEAs particles and aluminum matrix is smooth. At 500 °C, the intensity of HEAs diffraction peak in the composite material changes significantly. At 520 °C, AlNi solid solution phase with BCC structure appears in the HEAs region, and the HEAs structure changes from FCC to FCC + BCC, and Al5Cr8, Al5Co2 and Al2Cu phases precipitate. At 480 °C, the nanohardness and elastic modulus at the interface reaches 1245.31 MPa and 72.45 GPa, respectively, showing relatively excellent interfacial bonding strength. The elastic modulus of both HEAs reinforcement and aluminum matrix decrease at a sintering temperature above 480 °C, and the composites have hard and brittle characteristics. At 480 °C, the macroscopic compression and yield strengths of composites are ~ 421.2 MPa and ~ 289.5 MPa, and the maximum shrinkage rate is ~65.3%, exhibiting excellent strength and toughness.