Damping properties and mechanism of aluminum matrix composites reinforced with glass cenospheres

The damping properties were improved by preparing Al matrix composites reinforced with glass cenospheres through the pressure infiltration method.Transmission electron microscopy and scanning electron microscopy were employed to characterize the microstructure of the composites.The low-frequency damping properties were examined by using a dynamic mechanical thermal analyzer,aiming at exploring the changing trend of damping capacity with strain,temperature,and frequency.The findings demonstrated that the damping value rose as temperature and strain increased,with a maximum value of 0.15.Additionally,the damping value decreased when the frequency increased.Dislocation damping under strain and interfacial damping under temperature served as the two primary damping mechanisms.The increase in the density of dislocation strong pinning points following heat treatment reduced the damping value,which was attributed to the heat treatment enhancement of the interfacial bonding force of the composites.

Effect of Ni content on the wear behavior of Al-Si-Cu-Mg-Ni/SiC particles composites

In recent years,the addition of Ni has been widely acknowledged to be capable of enhancing the mechanical properties of Al-Si alloys.However,the effect of Ni on the wear behaviors of Al-Si alloys and Al matrix composites,particularly at elevated temperat-ures,remains an understudied area.In this study,Al-Si-Cu-Mg-Ni/20wt%SiC particles(SiCp)composites with varying Ni contents were prepared by using a semisolid stir casting method.The effect of Ni content on the dry sliding wear behavior of the prepared compos-ites was investigated through sliding tests at 25 and 350℃.Results indicated that theθ-Al_(2)Cu phase gradually diminished and eventually disappeared as the Ni content increased from 0wt%to 3wt%.This change was accompanied by the formation and increase inδ-Al_(3)CuNi andε-Al_(3)Ni phases in microstructures.The hardness and ultimate tensile strength of the as-cast composites improved,and the wear rates of the composites decreased from 5.29×10^(−4)to 1.94×10^(−4)mm^(3)/(N∙m)at 25℃and from 20.2×10^(−4)to 7×10^(−4)mm^(3)/(N∙m)at 350℃with the increase in Ni content from 0wt%to 2wt%.The enhancement in performance was due to the presence of strengthening network structures and additional Ni-containing phases in the composites.However,the wear rate of the 3Ni composite was approximately two times higher than that of the 2Ni composite due to the fracture and debonding of theε-Al_(3)Ni phase.Abrasive wear,delamination wear,and oxidation wear were the predominant wear mechanisms of the investigated composites at 25℃,whereas delamination wear and oxid-ation wear were dominant during sliding at 350℃.

Development of Al-12Si-xTi system active ternary filler metals for Al metal matrix composites

To improve the wettability of Al metal matrix composites（Al-MMCs） by common filler metals,Al-12Si-xTi（x=0.1,0.5,1,3.0;mass fraction,%） system active ternary filler metals were prepared.It was demonstrated that although the added Ti existed within Ti（Al1-xSix）3（0≤x≤0.15） phase,the shear strength and shear fracture surface of the developed Al-12Si-xTi brazes were quite similar to those of traditional Al-12Si braze due to the presence of similar microstructure of Al-Si eutectic microstructure with large volume fraction.So,small Ti addition（～1%） did not make the active brazes brittle and hard compared with the conventional Al-12Si braze.The measured melting range of each Al-12Si-xTi foil was very similar,i.e.,580-590 ℃,because the composition was close to that of eutectic.For wettability improvement,with increasing Ti content,the interfacial gap between the Al2O3 reinforcement and filler metal（R/M） could be eliminated,and the amount of the remainder of the active fillers on the composite substrate decreased after sessile drop test at 610 ℃ for 30 min.So,the wettability improvement became easy to observe repeatedly with increasing Ti content.Additionally,the amount and size of Ti（AlSi）3 phase were sensitive to the Ti content（before brazing） and Si content（after brazing）.

Microstructures and mechanical properties of BP/7A04 Al matrix composites

The microstructures and interface structures of basalt particle reinforced 7A04 Al matrix composites (BP/7A04 Al) were analyzed by using OM, TEM, SEM and EDS, and the mechanical properties of 7A04 Al alloy were compared with those of BP/7A04 Al matrix composites. The results show that the basalt particles are dispersed in the Al matrix and form a strong bonding interface with the Al matrix. SiO2 at the edge of the basalt particles is continuously replaced by Al2O3 formed in the reaction, forming a high-temperature reaction layer with a thickness of several tens of nanometers, and Al2O3 strengthens the bonding interface between basalt particles and Al matrix. The dispersed basalt particles promote the dislocation multiplication, vacancy formation and precipitation of the matrix, and the precipitated phases mainly consist of plate-like η(MgZn2) phase and bright white band-shaped or ellipsoidal T (Al2Mg3Zn3) phase. The bonding interface, high dislocation density and dispersion strengthening phase significantly improve the mechanical properties of the composites. The yield strength and ultimate tensile strength of BP/7A04 Al matrix composites are up to 665 and 699 MPa, which increase by 11.4% and 10.9% respectively compared with 7A04 Al alloy without basalt particles.

Microstructures and mechanical properties of Al 2519 matrix composites reinforced with Ti-coated SiC particles

Ti-coated SiCp particles were developed by vacuum evaporation with Ti to improve the interfacial bonding of SiCp/Al composites.Ti-coated SiC particles and uncoated SiC particles reinforced Al 2519 matrix composites were prepared by hot pressing,hot extrusion and heat treatment.The influence of Ti coating on microstructure and mechanical properties of the composites was analyzed by scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS).The results show that the densely deposited Ti coating reacts with SiC particles to form TiC and Ti5Si3 phases at the interface.Ti-coated SiC particle reinforced composite exhibits uniformity and compactness compared to the composite reinforced with uncoated SiC particles.The microstructure,relative density and mechanical properties of the composite are significantly improved.When the volume fraction is 15%,the hardness,fracture strain and tensile strength of the SiCp reinforced Al 2519 composite after Ti plating are optimized,which are HB 138.5,4.02%and 455 MPa,respectively.

Processing and mechanical properties of 2024 aluminum matrix composites containing Tungsten and Tantalum prepared by PM

The 2024 Al composites containing W, Ta were fabricated by powder metallurgy for their potential use as shielding material. W, Ta powders and gas-atomized 2024 Al aluminum powders were mixed by a ball mixer. The mixtures were consolidated by cold isostatic pressing (CIP) and then hot-extruded into full-density bars. The extruded bars were heat treated in T6 conditions. The microstructure and its relationship with the mechanical properties were investigated by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that the particles of nonuniform size and irregular shape randomly disperse in the 2024 aluminum alloy matrix. The tensile tests show that an increase of tensile strength and decrease of elongation to failure of the heat treated composites compared with the extruded composites.

Corrosion Behavior of SiC_p/2024 Al Matrix Composites in 3.5 wt pct Sodium Chloride

The influences of volume fraction and particle size of SiC particulate reinforcements on the corrosion characteristics of SiCp/2024 Al metal matrix composites in aerated 3.5 wt pct NaCI aqueous solution were investigated. The electrochemical behavior was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy, the general corrosion behavior of the composites was studied further by immersion tests. The results showed that pitting susceptibility was about the same for the composites and the alloy. The corrosion potentials were also independent of SiC phase. The corrosion resistance for the composites decreased as the volume fraction increased or particle size decreased.

Compositing Soft Coated Ti-Fiber Reinforced Ti-Al Matrix Composites

It is showed that there are Ti 3Al, Ti 2Cu and β phase in the interface of Ti/Ti Al composites reinforced with Y 2O 3 Cr composite soft coated Ti fiber, and that interface bonding is intact. Bending strength of the composites can be increased by 26%, to 709 MPa, and bending deflection increased slightly compared with the Ti/Ti Al composites reinforced by Ti fibers coated with Y 2O 3.

Effect of Interfacial Bonding on the Toughening of Al_2O_3/Ni Ceramic Matrix Composites

The main Iimitation to the toughening of the α-Al2O3/Ni composite is the poor bonding atthe interface. which causes the nickel particles to be pulled-out during crack propagation with-out obvious plastic deformation. A proper control of oxygen content at the Al2O3-Ni interfacecan promote wetting at the intedece, and produce a mechanically interlocked and chemically strengthened intedece, causing most of the nickel particles to be stretched to failure and to expe-rience severe plastic deformation during crack propagation in the composite. Fracture toughnesstesting using a modified double cantilever beam method with in situ observation of crack prop-agation in a scanning electron microscope shows that the composite with the strengthenedinterface has a more desirable R-curve behaviour and a higher fracture toughness value than thenormal composite.

Effect of heat treatment on microstructure and thermophysical properties of diamond/2024 Al composites

50%diamond particle （5μm） reinforced 2024 aluminum matrix （diamond/2024 Al） composites were prepared by pressure infiltration method. Diamond particles were distributed uniformly without any particle clustering, and no apparent porosities or significant casting defects were observed in the composites. The diamond-Al interfaces of as-cast and annealed diamond/2024 Al composites were clean, smooth and free from interfacial reaction product. However, a large number of Al2Cu precipitates were found at diamond-Al interface after aging treatment. Moreover, needle-shaped Al2MgCu precipitates in Al matrix were observed after aging treatment. The coefficient of thermal expansion （CTE） of diamond/2024 Al composites was about 8.5×10-6 °C-1 between 20 and 100 °C, which was compatible with that with chip materials. Annealing treatment showed little effect on thermal expansion behavior, and aging treatment could further decrease the CTE of the composites. The thermal conductivity of obtained diamond/2024 Al composites was about 100 W/（m？K）, and it was slightly increased after annealing while decreased after aging treatment.

Preparation and Mechanical Properties of-SiC Nanoparticle Reinforced Aluminum Matrix Composite by a Multi-step Powder Metallurgy Process

β-SiC nanoparticle reinforced A1 matrix （nano-SiCp/A1） composite was prepared by a multi- step powder metallurgy strategy including presureless sintering, hot compacting process and hot extrusion. The microstructures of the as-prepared composites were observed by scanning electronic microscopy （SEM）, and the mechanical properties were characterized by tensile strength measurement and Brinell hardness test. The experimental results revealed that the tensile strength of the composite with the addition of 5wt%/3-SIC nanoprtieles could be increased to 215 MPa, increasing by 110% compared with pure A1 matrix. Comparative experiments reflected that theβ-SIC nanoprticles showed significant reinforcement effect than traditional a-SiC micro-sized particles. The preparation process and sintering procedure were investigated to develop a cost effective preparation strategy to fabricate nano-SiCp/A1 composite.

Effects of Cu content on microstructures and compressive mechanical properties of CNTs/Al-Cu composites

The carbon nanotubes(CNTs) reinforced Al-Cu matrix composites were prepared by hot pressing sintering and hot rolling, and the effects of Cu content on the interfacial reaction between Al and CNTs, the precipitation behavior of Cu-containing precipitates, and the resultant mechanical properties of the composites were systematically investigated. The results showed that the increase of Cu content can not only increase the number and size of Cu-containing precipitate generated during the composite fabrication processes, but also promote the interfacial reaction between CNTs and Al matrix, leading to the intensified conversion of CNTs into Al_(4)C_(3). As a result, the composite containing 1 wt.% Cu possesses the highest strength, elastic modulus and hardness among all composites, due to the maintenance of the original structure of CNTs. Moreover, the increase of Cu content can change the dominant strengthening mechanisms for the enhanced strength of the fabricated composites.

Improvement of high-temperature strength of 6061 Al matrix composite reinforced by dual-phased nano-AlN and submicron-Al_(2)O_(3)particles

Nano-AlN and submicron-Al_(2)O_(3) particles were simultaneously utilized in a 6061 Al matrix composite to improve the high-temperature strength.According to the SEM and TEM characterization,nano-AlN and submicron-Al_(2)O_(3) particles are uniformly distributed in the Al matrix.Brinell hardness results indicate that different from the traditional 6061 Al matrix alloy,the aging kinetics of the composite is obviously accelerated by the reinforcement particles.The T6-treated composite exhibits excellent tensile properties at both room temperature and elevated temperature.Especially at 350℃,the T6-treated composite not only has a high yield strength of 121 MPa and ultimate tensile strength of 128 MPa,but also exhibits a large elongation of 11.6%.Different strengthening mechanisms of nano-AlN and submicron-Al_(2)O_(3) particles were also discussed in detail.

Effect of carbon content on microstructure of in-situ Al_2O_(3p)-TiC_p/Al composites

The in situ Al 2O 3p TiC p/Al composite was fabricated by XD (exothermic dispersion) process in TiO 2 Al C system, and the effect of carbon content on the microstructure of the fabricated composite and the reactive temperature characteristics had been studied. The results show that carbon content affects the microstructure and reactive temperature of Al 2O 3p TiC p/Al composite greatly. The quantity of TiC phases in the fabricated composites increases, while the Al 3Ti phases reduces with increasing carbon content. And when C/TiO 2 molecular ratio is equal to one, the Al 3Ti phase nearly disappears. High temperature metallurgical field caused by strong exothermic reaction influences the synthetic reaction greatly, and higher synthetic temperature was favorable to the synthesis of Al 2O 3p TiC p reinforce particles.

Effects of whisker surface treatment on microstructure and properties of Al_(18)B_4O_(33w)/6061Al composites

6061Al matrix composites reinforced by ZnO-coated Al18B4O33 whiskers were fabricated by a semi-solid mechanical stirring technique.The effects of ZnO coating on interfacial reaction between whiskers and matrix and the tensile properties of the composites were investigated.Tensile tests on composites were performed at room temperature,and microstructures were observed by scanning electron microscopy(SEM).The results show that the surface treatment of whiskers could reduce interfacial reaction effectively,improve the wettability between whiskers and matrix and enhance the tensile properties of the composites obviously.In addition,semi-solid stirring parameters were also under preliminary study.The stirring parameters were determined by the distribution of whiskers in the composites.The composites with homogeneously distributed whiskers were fabricated by semi-solid stirring at 610 ℃ for 30 min.

Microstructure and Mechanical Properties of AlSiTiCrNiCu Particles Reinforced Al6061 Composites by SPS and HPS Process

Three groups of AlSiTiCrNiCu high entropy alloy(HEA)particles reinforced Al606l composites were fabricated by spark plasma sintering at 520 and 570℃(S520,S570)and by hot-pressed sintering at 570℃(H570).The AlSiTiCrNiCu(AST)particles used as reinforcements were synthesized by mechanical alloying.The influences of the sintering process on the microstructure and mechanical properties of composites were investigated.The results showed that the AST particles had a near-equiatomic composition with a single BCC structure.The sintering temperature and time had a coupling influence on the interfacial microstructure.S520 had hardly reaction products and slight interfacial diffusion,and the AST particles were completely high entropy.Intense interfacial reactions happened on S570 and H570 with the same reaction products.The element diffusion of S570 was focused on the edge of the AST particles with partial loss of high entropy.Complete element diffusion and entire loss of high entropy of AST particles happened on H570.The differences in the microstructure caused by the three preparation methods led to the changes in mechanical properties and fracture mechanisms of composites.

JOINING MECHANISMS OF β"-Al_2O_3 CERAMIC AND PYREX GLASS TO Al MATRIX COMPOSITE

The bonding of β″-Al2O3 and pyrex glass to A1 matrix composites by anodic bonding process is achieved. The microstructure of the bonded interface and the joining mechanisms are analyzed with scanning electron microscope （SEM）, energy dispersive X-ray fluorescence spectrometer （EDX）. It is observed that the bonding region across the interface consists of the metal layer, oxide transitional layer and the ceramic layer, with the transitional layer composed of surface region and sub-surface region. The bonding process can mainly be categorized into anodic bonding process and solid state diffusing process. The pile-up of the ions and its drift in the interface area are the main reasons for anode oxidation and joining of the interface. The temperature, voltage and the drift ions in the ceramic or glass during the bonding process are the essential conditions to solid state diffusing and oxide bonding at the interface. The voltages, temperature, pressure as well as the surface state are the main factors that influence the anodic bonding.

THE INTERFACIAL BEHAVIORS OF ALUMINUM MATRIX COMPOSITE IN DIFFERENT WELDING METHODS

Non-interlayer liquid phase diffusion welding (China Patent) and laser welding methods for aluminum matrix composite are mainly described in this paper. In the non-interlayer liquid phase diffusion welding, the key processing parameters affecting the strength of joint is welding temperature. When temperature rises beyond solidus temperature, the bonded line vanishes. The strength of joint reaches the maximum and becomes constant when welding temperature is close to liquid phase temperature. Oxide film in the interface is no longer detected by SEM in the welded joint. With this kind of technique, particle reinforced aluminum matrix composite Al2 O3p/6061Al is welded successfully, and the joint strength is about 80% of the strength of composite (as-casted). In the laser welding, results indicate that because of the huge specific surface area of the reinforcement, the interfacial reaction between the matrix and the reinforcement is restrained intensively at certain laser power and pulsed laser beam. The laser pulse frequency directly affects the reinforcement segregation and the reinforcement distribution in the weld, so that the weldability of the composite could be improved by increasing the laser pulse frequency. The maximum strength of the weld can reach 70% of the strength of the parent.

MECHANICAL PROPERTIES AND INTERFACIAL STRUCTURES OF ALUMINIUM BORATE WHISKER REINFORCED ALUMINIUM COMPOSITES

Quality 9Al_2O_3-2B_2O_3 whisker reinforced 6061Al or Al composites have been prepared by technique of squeeze casting.The mechanical properties of the 9Al_2O_3·2B_2O_3(w)/6061Al composites could be hardly improved by T6 treatment,owing to cause the remarkable interracial reaction.An observation under high resolution trans- mission electron microscope on interfaces shows that the serious chemical reaction occurs and the product is Al_2MgO_4.But no such reaction is found at the interfaces of 9Al_2O_3. 2B_2O_3(w)/Al composite.EDS analysis on the interfaces shows that above mentioned interracial reaction may be resulted from the interracial segregation of Mg atoms in 6061Al matrix during sequeeze casting.

Superplasticity of a SiCw/Zn-22Al Composites

In this paper, the superplastic characteristics of a 15 SiC(vol. pct) whisker reinforced Zn-22AI alloy composites, fabricated by low pressure infiltration and solute treatment after extrusion with the extrusion rate of 10:1, was investigated. The result showed that the composite exhibited a tensile elongation of 150% and a strain rate sensitivity value of about 0.33 at the initial strain rate of 6.67×10-2 s-1 and at 658 K where an appropriate amount of liquid phase was presented in the composite.