Wedge BUE of SiC reinforced aluminium composites

Several orthogonal cutting experiments were carried out on SiC reinforced aluminium composites. In the cutting process, photos of the chip bottom specimen SEM were gotten with the aid of ‘quick stop tool device’. According to the photos, the build up edge (BUE) can be produced in circumferential cutting experiments. In comparison with carbon steel BUE, aluminium composites BUE is like a wedge in shape, and its development mechanism is mechanical enchasing other than "cold welding". In addition to the above mentioned conclusions, the minishing BUE height H b is also analyzed.

Influence of DC Current on Corrosion Behaviour of Copper–Aluminium Composite Plates

In this study, neutral salt spray accelerated corrosion test of copper–aluminium composite under 0–125 A DC current was carried out under 5% concentration. The effect of corrosion behaviour on copper–aluminium composite by DC current was carried out by a scanning electron microscope(SEM) with energy-dispersive spectroscopy(EDS), X-ray diffraction(XRD) patterns, X-ray photoelectron spectroscopy(XPS), weight-loss method and electrochemical analysis. The results show that the current can accelerate the corrosion rate. Meanwhile, the current temperature effect can reduce the corrosion rate. The current caused directional migration of ions resulting in different corrosion products on positive and negative poles of specimen, and the corrosion degree on the positive pole was more serious. The galvanic corrosion mechanism at the copper–aluminium interface is different from the pitting corrosion mechanism far away from the interface, and the latter is more affected by DC current.

Features of microstructure and fracture in the transient liquid phase bonded aluminium-based metal matrix composite joints

Transient liquid phase (TLP) bonded aluminium based metal matrix composite (MMC) joints can be classified into three distinct regions, i.e. the particulate segregation region, the denuded particulate region and the base material region. The microstructure of the particulate segregation region consists of alumina particulate and Al alloy matrix with the Al 2Cu and MgAl 2O 4. It contains more and smaller alumina particulates compared with the base material region. The TLP bonded joints have the tensile strength of 150 MPa ～200 MPa and the shear strength of 70 MPa ～100 MPa . With increasing tensile stress, cracks initiate in the particulate segregation region, especially in the particulate/particulate interface and the particulate/matrix interface, and propagate along particulate/matrix interface, througth thin matrix metal and by linking up the close cracks. The particulate segregation region is the weakest during tensile testing and shear testing due to obviously increased proportion of weak bonds (particulate particulate bond and particulate matrix bond).

A review of tool wear prediction during friction stir welding of aluminium matrix composite

Friction stir welding is the preferred joining method for aluminium matrix composites. It is a solid-state process which prevents the formation of the intermetallic precipitates responsible for degradation of mechanical properties in fusion welds of these composites. The major concern in friction stir welding is the wear of the welding tool pin. The wear is due to the prolonged contact between the tool and the harder reinforcements in the composite materials. This paper provides an overview of the effects of different parameters of friction stir welding on the tool wear. It was found that the total amount of material removed from the tool is in directproportion to the rotational speed of the tool and the length of the weld but inversely proportional to the transverse rate. The result seven demonstrate that the tool geometry also has significant influence on the wear resistance of the tool. The tool even converts itself into a self-optimized shape to minimize its wear.

Interface reaction in aluminium matrix composite at laser welding

Interface reaction of SiC w/6061Al aluminium matrix composite subjected to laser welding was studied. It is pointed out that the main reason for bad weldability of the material is concerned with the interface reaction during the welding. Effects of welding parameters on interface reaction were also investigated. The results show that the interface bonding state can be improved by laser beam, and the main welding parameter affecting the strength of weld is laser output power. The smaller the output power, the lower the extent of interface reaction and the better the mechanical properties.

Study on Diffusion Welding Parameters of Particle reinforced Aluminium Matrix Composite Al_2O_(3p) /6061Al

Effects of diffusion welding process parameters on strength of welded joint based on particle reinforced aluminium matrix composite Al 2O 3p /6061Al have been studied through comparing with aluminium matrix alloy. The mechanism for loss of joint strength has been analyzed. It should be pointed out that key processing parameters affecting the strength of joint was welding temperature. The high quality joint can be successfully obtained with appropriate diffusion welding parameters.

Effect of Ti-Si-Mg-Al wire on microstructure and mechanical properties of plasma arc in-situ welded joint of SiC_p/Al composites

The influence of Ti-Si-Mg-AI wire on microstructure and mechanical properties of SiCp/A1 metal matrix composite joints produced by plasma arc in-situ weld-alloying was investigated. Argon-nitrogen mixture was used as plasma gas and Ti-Si-Mg-A1 flux-cored wires as filled composites. Weldments were submitted to tensile test. Meanwhile, the macro morphology and microstructure of the joints were examined. The result shows that the formation ofneedie-like harmful phase A14C3 is effectively inhibited and the wettability of molten pool is improved by adding Ti-Si-Mg-A1 flux-cored wires. With 15Ti-5Si-5Mg-A1 flux-cored wire as filled composite, the maximum tensile strength of the welded joint is 267 MPa, which is up to 83% that of the matrix composites under annealed condition.

Effect of laser surface melting on surface integrity of Al-4.5Cu composites reinforced with SiC and MoS2

Two types of composites were prepared with Al-4.5Cu alloy as a matrix using stir casting method.One was reinforced with 10wt.%of Si C and 2wt.%of MoS2.The other was reinforced with 10wt.%of Si C and 4wt.%of MoS2.Their surfaces were remelted using a CO2 laser beam with an objective to study the influence of laser surface melting(LSM).The topography,microhardness,corrosion resistance and wear resistance of the laser melted surfaces were studied.Overall surface integrity after LSM was compared with as-cast surface.LSM enhanced the microhardness and wear resistance of the surface in each case.Porosity of the laser melted surface was low and corrosion resistance was high.Thus,LSM can be conveniently applied to enhancing the surface integrity of the aluminium composites.However,there is an optimum laser specific energy,around 38 J/m^2 in this study,for obtaining the best surface integrity.

Comparison of wear behaviour of LM13 Al−Si alloy based composites reinforced with synthetic(B_(4)C)and natural(ilmenite)ceramic particles

Dry sliding wear behaviour of stir-cast aluminium matrix composites(AMCs)containing LM13 alloy as matrix and ceramic particles as reinforcement was investigated.Two different ceramic particle reinforcements were used separately:synthetic ceramic particles(B_(4)C),and natural ceramic particles(ilmenite).Optical micrographs showed uniform dispersion of reinforced particles in the matrix material.Reinforced particles refined the grain size of eutectic silicon and changed its morphology to globular type.B_(4)C reinforced composites(BRCs)showed maximum improvement in hardness of AMCs.Ilmenite reinforced composites(IRCs)showed maximum reduction in coefficient of friction values due to strong matrix−reinforcement interfacial bonding caused by the formation of interfacial compounds.Dry sliding wear behaviour of composites was significantly improved as compared to base alloy.The low density and high hardness of B_(4)C particles resulted in high dislocation density around filler particles in BRCs.On the other hand,the low thermal conductivity of ilmenite particles resulted in early oxidation and formation of a tribo-layer on surface of IRCs.So,both types of reinforcements led to the improvement in wear properties of AMCs,though the mechanisms involved were very different.Thus,the low-cost ilmenite particles can be used as alternative fillers to the high-cost B_(4)C particles for processing of wear resistant composites.

Al-Si/Al_2O_3 in situ composite prepared by displacement reaction of CuO/Al system

Al2O3 particle-reinforced ZL109 composite was prepared by in situ reaction between CuO and Al2O3 . The microstructure was observed by means of OM, SEM and TEM. The Al2O3 particles in sub-micron sizes distribute uniformly in the matrix, and the Cu displaced from the in situ reaction forms net-like alloy phases with other alloy elements. The hardness and the tensile strength of the composites at room temperature have a slight increase as compared to that of the matrix. However, the tensile strength at 350℃ has reached 90.23 MPa, or 16.92 MPa higher than that of the matrix. The mechanism of the reaction in the CuO/AI system was studied by using of differential scanning calorimetry（DSC） and thermodynamic calculation. The reaction between CuO and Al involves two steps. First, CuO reacts with Al to form Cu20 and Al2O3 at the melting temperature of the matrix alloy, and second, Cu20 reacts with Al to form Cu and Al2O3 at a higher temperature. At ZL109 casting temperature of 750- 780 ℃, the second step can also take place because of the effect of exothermic reaction of the first step.

Study on behavior of reinforcement in molten pool for submicron composite Al_2O_3p/6061 Al during laser welding

The behavior of the reinforcement of submicron composite Al_ 2 O_ 3 p/6061Al in molten pool during laser welding was studied. It was indicated that because there were the remarkable differences in thermal physical properties between matrix and reinforcement particulate, the reinforced particulate was pushed forward during molten pool solidification by the liquid-solid interface in matrix and the reinforced particulate segregated in the weld. It resulted in noticeable degradation in properties of the welded joint. The technology methods to improve the behavior of reinforcement were also investigated. It was pointed out that the laser pulse frequency is the main welding parameter affecting the distributive state of reinforcement, and the theory basis was established for welding the material by laser beam.

STUDY ON DIFFUSION WELDING OF ALUMINIUN MATRIX COMPOSITE

Effects of diffusion welding parameters on strength of welded joint based on particle reinforced alumini- um matrix composite Al2O3p/6061Al were studied by comparing with aluminium matrix alloy,Mecha- nism for the loss of joint strength was analyzed.It was pointed out that the key processing parameters affecting the strength of joint was the welding temperature.The high quality joint can be successfully obtained with appropriate diffusion welding parameters.

SOLIDIFICATION MECHANISM OF Al/TiC INTRAGRANULAR COMPOSITES FABRICATED BY CONTACT REACTION METHOD

The behaviour of the particles in solidification inter face front was studied, and the equation of the critical interface velocity which related to the supercooling and the volume fraction of particles in the melt was obtained. By the mean time, the two solidification mechanisms of aluminium matrix intragranular composites was put forward.

Ductility and hardness of chloride cleaned AA6011/SiC_p composites

Theductility and hardness of AA6011/SiCp composites using NaCl, SnCl2, NH4Cl and PdCl2 as wetting reagents were investigated. SiCp was cleaned with the wetting reagents, and used as reinforcement in AA6011 alloy using the stir casting method. Ductility and hardness responses of the composites were measured using standard methods. Microstructural features were examined using scanning electron microscopy and the phases were determined with the help of an X-ray diffractometer. The results show that for all wetting agents, the increase in cleaning time leads to initial increase in ductility to a certain value, but a decrease afterwards with further increase in cleaning time. The best combination of hardness （BHN 57.88） and ductility （11.91%） was shown under conditions of 40 g/L SnCl2and cleaning time of 60 min. A minor formation of Al4C3was noted in diffraction patterns, indicating that the formation of deleterious precipitate was hindered by the cleaning process.

Dry sliding wear behavior of stir cast AA6061-T6/AlN_p composite

The dry sliding wear behavior of AA6061 matrix composite reinforced with aluminium nitride particles（AlN） produced by stir casting process was investigated. A regression model was developed to predict the wear rate of the prepared composite. A four-factor, five-level central composite rotatable design matrix was used to minimize the number of experimental runs. The factors considered in this study were sliding velocity, sliding distance, normal load and mass fraction of AlN reinforcement in the matrix. The developed regression model was validated by statistical software SYSTAT 12 and statistical tools such as analysis of variance（ANOVA） and student＇s t test. It was found that the developed regression model could be effectively used to predict the wear rate at 95% confidence level. The influence of these factors on wear rate of AA6061/AlNp composite was analyzed using the developed regression model and predicted trends were discussed with the aid of worn surface morphologies. The regression model indicated that the wear rate of cast AA6061/AlNp composite decreased with an increase in the mass fraction of AlN and increased with an increase of the sliding velocity, sliding distance and normal load acting on the composite specimen.

Mechanical properties and fracture mechanisms of aluminum matrix composites reinforced by Al_9(Co,Ni)_2 intermetallics

The microstructures and mechanical properties of Al matrix composites reinforced by different volume fractions of Al-Ni-Co intermetallic particles were investigated.Three different volume fractions of Al-Ni-Co particles were added to pure Al matrix using a stir-casting method.Microstructural analysis shows that with the increasing of the reinforcement volume fraction,the matrix grain size decreases and the porosity increases.The mechanical properties of the composites are improved over the matrix materials,except for the decreasing of the ductility.Fracture surface examination indicates that there is a good interfacial bonding between the Al matrix and the Al-Ni-Co particles and the fracture initiation does not occur at the particle-matrix interface.

Dry sliding wear characterization of Al 6061/rock dust composite

The influence of rock dust size（10-30 μm） and mass fraction（5%-15%） on density, hardness and dry sliding wear behavior of Al 6061/rock dust composite processed through stir casting was investigated. Wear behavior of the developed composite was characterized at different loads, sliding velocities and distances using pin-on-disc setup. The experiments were conducted based on Taguchi＇s L27 orthogonal array and the influence of process parameters on wear rate was studied using ANOVA. The experimental results reveal that the applied load and reinforcement size are the major parameters influencing the specific wear rate for all samples, followed by mass fraction of reinforcement, sliding velocity and sliding distance at the level of 47.61%, 28.57%, 19.04%, 9.52% and 4.76%, respectively. The developed regression equation was tested for its accuracy and made evident that it can be used for predicting the wear rate with minimal error. With the help of SEM images, the worn surfaces of the novel composite were studied and the analysis proves that the wear resistance of aluminium alloys can be well improved with the addition of rock dust as reinforcement.

Compression Mechanical Behaviour of 7075 Aluminium Matrix Composite Reinforced with Nano-sized SiC Particles in Semisolid State

The 7075 aluminium matrix composite reinforced with nano-sized Si C particles was fabricated by ultrasonic assisted semisolid stirring method. The compression mechanical behaviour of the fabricated composite in semisolid state was investigated. The results show that the microstructure of the composite before semisolid compression consists of fine and spheroidal solid grains surrounded by liquid phase.Semisolid compression led to a nonuniform plastic deformation of solid grains. A slight plastic deformation occurred in the locations near the free surface due to the dependence of deformation on liquid flow and flow of liquid incorporating solid grains. However, obvious plastic deformation occurred in the central location and location contacting to die due to the contribution of plastic deformation of solid grains.The true stress–strain curve of the sample compressed at 500 °C consists of rapid increase of true stress and steady stage. However, rapid increase of true stress and decrease of true stress and steady stage are involved in the true stress–strain curves of the samples compressed at 550, 560, 570, 580 and 590 °C.The true stress–strain curve at 600 °C is similar to that at 500 °C. Apparent viscosity decreases with an increase of shear rate, indicating a shear thinning occurrence. When soaking time increases from 5 min to 15 min, the peak stress and steady stress decrease significantly. A further increase of the soaking time led to a slight change. Peak stress and steady stress increase with increasing volume fraction of Si C particles. A sudden increase or decrease of compression velocity led to a significant increase or decrease of the steady stress. The destruction of the samples compressed at solid state temperature mainly depends on cracks parallel to compression direction. However, the destruction forms of the samples compressed at semisolid temperatures consist of cracks parallel to compression direction and partial collapse. Increasing soaking time led to an obvious change of the destruction forms. Compression velocity affects slightly the macro appearance of the sample compressed at semisolid temperatures.

Effect of process parameters on the density and porosity of laser melted AlSi10Mg/SiC metal matrix composite

Laser melting of aluminium alloy-AlSi10Mg has increasingly been used to create specialised products in various industrial applications, however, research on utilising laser melting of aluminium matrix composites in replacing specialised parts have been slow on the uptake. This has been attributed to the complexity of the laser melting process, metal/ceramic feedstock for the process and the reaction of the feedstock material to the laser. Thus, an understanding of the process, material microstructure and mechanical properties is important for its adoption as a manufacturing route of aluminium metal matrix composites. The effects of several parameters of the laser melting process on the mechanical blended composite were thus investigated in this research. This included single track formations of the matrix alloy and the composite alloyed with 5% and 10% respectively for their reaction to laser melting and the fabrication of density blocks to investigate the relative density and porosity over different scan speeds. The results from these experiments were utilised in determining a process window in fabricating near-fully dense parts.

Synchrotron Characterisation of Ultra-Fine Grain TiB_(2)/Al-Cu Composite Fabricated by Laser Powder Bed Fusion

Isotropy in microstructure and mechanical properties remains a challenge for laser powder bed fusion(LPBF)processed materials due to the epitaxial growth and rapid cooling in LPBF.In this study,a high-strength TiB_(2)/Al-Cu composite with random texture was successfully fabricated by laser powder bed fusion(LPBF)using pre-doped TiB_(2)/Al-Cu composite powder.A series of advanced characterisation techniques,including synchrotron X-ray tomography,correlative focussed ion beam-scanning electron microscopy(FIB-SEM),scanning transmission electron microscopy(STEM),and synchrotron in situ X-ray diffraction,were applied to investigate the defects and microstructure of the as-fabricated TiB_(2)/Al-Cu composite across multiple length scales.The study showed ultra-fine grains with an average grain size of about 0.86μm,and a random texture was formed in the as-fabricated condition due to rapid solidification and the TiB_(2)particles promoting heterogeneous nucleation.The yield strength and total elongation of the as-fabricated composite were 317 MPa and 10%,respectively.The contributions of fine grains,solid solutions,dislocations,particles,and Guinier-Preston(GP)zones were calculated.Failure was found to be initiated from the largest lack-of-fusion pore,as revealed by in situ synchrotron tomography during tensile loading.In situ synchrotron diffraction was used to characterise the lattice strain evolution during tensile loading,providing important data for the development of crystal-plasticity models.