Preparation technique of SiCp reinforced Al matrix composite

The advancement of modern technology in the areas of aerospace and automotive industries has generated demand for new engineering materials, leading to a rapid development of metal matrix composites (MMCs) [1]. These composites can be tailored to have outstanding mechanical and physical properties such as high specific strength and stiffness, increased wear resistance, enhanced high-temperature performance and better thermal, mechanical fatigue and creep resistance than those of monolithic mat…     

Effects of particle size on residual stresses of metal matrix composites

A finite element analysis was carried out on the development of residual stresses during the cooling process from the fabrication temperature in the SiCp reinforced AI matrix composites. In the simulation, the two-dimensional and random distribution multi-particle unit cell model and plane strain conditions were used. By incorporating the Taylor-based nonlocal plasticity theory, the effect of particle size on the nature, magnitude and distribution of residual stresses of the composites was studied. The magnitude thermal-stress-induced plastic deformation during cooling was also calculated. The results show similarities in the patterns of thermal residual stress and strain distributions for all ranges of particle size. However, they show differences in magnitude of thermal residual stress as a result of strain gradient effect. The average thermal residual stress increases with decreasing particle size, and the residual plastic strain decreases with decreasing particle size.     

Self-propagating high temperature synthesis of MoSi2 matrix composites

MoSi2 is presently regarded as the most important material for electrical heating and as one with huge potential for high temperature structural uses. MoSi2 and MoSi2 matrix composites were prepared by self-propagating high temperature synthesis （SHS）. Pure MoSi2 was obtained and a compound of MoSi2 and WSi2was synthesized in the form of predominant solid solution （Mo,W）Si2. By adding aluminum of 5.5 at.% to Mo-Si, the crystal structure of MoSi2 changed into a mixture of tetragonal Cllb MoSi2and hexagonal C40 Mo（Si,Al）2. The （Mo,W）Si2-Mo（Si,Al）2-W（Si,Al）2 composite materials were synthesized by adding aluminum of 5.5 at.% to Mo-W-Si. However, if the amount of the added aluminum was not larger than 2.5 at.%, it did not have any significant effect. SHS is an effective technology for synthesis of MoSi2 and MoSi2 matrix composites.     

Minimum norm method of analyzing ill-conditioned state of design matrix in estimation of parameters

1　INTRODUCTIONThestructureofanormalmatrixNisofill con ditionedstateifitisofstrongmulti collinearity ,andtheNwillaffectthequalityofLSestimationofpa rameters[13] .Whentheill conditionedstateisseri ous ,changealittleintheseriesofobservationcausedbyerrorwillmakethecorrespondingestimatesofLSestimationchangealot.So ,objectivelydecidingthemulti collinearityoftheNisespeciallyimportant .ThematrixNconditionnumberisincommonlyusedtomeasurethemulti collinearity[4 6 ] .TheNcondi tionnumberisdefine…     

Fabrication of aluminum matrix composite reinforced with carbon nanotubes

1.0wt.% carbon nanotube （CNT） reinforced 2024Al matrix composite was fabricated by cold isostatic press and subsequent hot extrusion techniques. The mechanical properties of the composite were measured by a tensile test. Mean-while,the fracture surfaces were examined using field emission scanning electron microscopy. The experimental results show that CNTs are dispersed homogeneously in the composite and that the interfaces of the Al matrix and the CNT bond well. Although the tensile strength and the Young’s modulus of the composite are enhanced markedly,the elongation does not decrease when compared with the matrix material fabricated under the same process. The reasons for the increments may be the extraordinary mechanical properties of CNTs,and the bridging and pulling-out role of CNTs in the Al matrix composite.     

Influence of microcrystalline wax on properties of MIM multi-component wax matrix binder

The properties of PW-EVA-HDPE binder with the addition of MW were studied. It shows that the addition of MW from 1% to 20%(mass fraction) causes an increase in the tensile strength and a decrease in shrinkage of the binder. After blending PW with MW, the crystallation behavior of wax base changes, which results in fine grain for the binder and more isotropic microstructure for the feedstock. The powder loading capacity increases and homogeneity of feedstock becomes better. The reason of the modification is also discussed.     

Thixoforming of SiC ceramic matrix composites in pseudo-semi-solid state

1INTRODUCTIONIt has great economic profit to exploit the uti-lization of SiC ceramic material for its strength,hardness,wear resistance,corrosion resistanceand high temperature resistance,abundant re-source and low price.But the brittle charactergreatly restricts its application in the field of engi-neering structure materials.Recently a series ofceramic matrix composites with exi mious perform-ance have been developed by reinforcing the matrixmaterial with other materials.Al/SiC is a la…     

Hot deformation and processing maps of titanium matrix composite

The hot deformation characteristics of TiC particles reinforced titanium matrix composite were studied in the temperature range from 900 ℃ to 1 150℃ and in the strain rate range of 10-3-10 s i by compression tests with Gleeblel500 simulator system. The flow behavior was described by the hyperbolic sine constitutive equation, and an average activation energy of 436.72 kJ/mol was calculated. The processing maps were calculated and analyzed according to the dynamic materials model. The maps show domains in some combinations of temperatures and strain rates and these domains are correlated with specific microstructural processes occurring during hot deformation by metallographic investigations and kinetic analysis. At the low strain rate domain occurs in the temperature range of 900-960 ℃ and strain rate range of 0.001-0.03 s^-1 superplasticity and dynamic recrystallization were observed. At a high strain rate domain occurs in the temperature range of 980-1 120 ℃ and strain rate range of 0.1-10 s^-1 the ,8 phase undergoes dynamic recrystallization. Also, at a strain rate range of 0.1-10 s^-1 and the temperature range of 900-930℃, the material exhibits flow localization.     

Influence of microcrystalline wax on properties of MIM multi-component was matrix binder

The properties of PW-EVA-HDPE binder with the addition of MW were studied.It shows that the addition of MW from 1% to 20%(mass fraction)causes an increase in the tensile strength and a decrease in shrinkage of the binder.After blending PW with MW,the crystallation behavior of wax base changes,which results in fine grain for the binder and more isotropic microstructure for the feedstock.The powder loading capacity increases and homogeneity of feedstock becomes better.The reason of the modification is also discussed.     

Modeling of effects of matrix on actuation characteristics of embedded shape memory alloy wires

1 INTRODUCTIONOne major application field of shape memoryalloys(SMAs) is the so-called smart structures .Numerous researches have been done on the actua-tion abilities of SMAs ,andthe results are quitein-spiring[1 ,2]. However , the complicated behaviorsof SMAs are still not fully understood, which pre-vents SMAs frombeing further adopted in real in-dustrial structures . The difficulties in understand-ing the SMAs mainly come fromthe fact that thetransformation and thus the actuatio…     

The structure of individual macromolecules of butadiene–styrene copolymers in polystyrene matrix

Radial-density distribution functions of segments and radii of gyration are obtained for the first time with the example of systems of statistical butadiene–styrene rubber of different composition and polystyrene by the processing of electron-microscopy images of individual copolymer molecules. Linear correlation dependences of R = f(M ^1/2) are plotted. The possibility of quantitative determination of fluctuation deviation from the equilibrium radius value is demonstrated. A method of calculating the values of Flory–Huggins parameters for individual macromolecules and their assembly is suggested.     

Effect of heat-treatment on microstructure and properties of SiC particulate-reinforced aluminum matrix composite

The effects of solid solution and aging processing on the microstructures and mechanical properties of the multi-layer spray co-deposited 7090Al/SiCp composite were investigated. The experimented results show that fine grains and homogeneous microstructures can be obtained, the average grain size of the as-solid solution treated and as-aged composites after extrusion is under 3.0μm. A large amount of the Cu-rich phase particles form in the as-extruded samples, and solve into the matrix after solid solution treatment. After aging, the size of the precipitate phases, mainly MgZn2 and CuAl2 is less than 1.0 μm, which homogeneously distribute inside the grains and at the grain boundaries. The ultimate tensile strength of the composite treated at T6 state, i.e. solid solution treated at 475 ℃for 1 h then aged at 120 ℃ for 24 h, is up to 765 MPa.     

Review on preparation techniques of particle reinforced metal matrix composites

The need for new engineering materials with theadvancement of modern technology in the areas ofaerospace, automotive and numerous other industries haslead to a rapid development of metal matrix composites(MMCs) [1]. They can be tailored to have outstandingmechanical and physical properties such as high specificstrength and stiffness, good wear resistance, enhancedhigh-temperature performance, and better thermal andmechanical fatigue and creep-resistance than that ofmonolithic materials. Among…     

Simulation of local effect of reinforcement on temperature field during solidification of aluminum metal matrix composite

The effect of reinforcement on the solidification of pure metal matrix composites （MMCs） was simulated using a two-dimensional solidification temperature field model by the finite element method. The concept of the character length was proposed to describe the size of reinforcement local heat influential zone in MMCs solidification according to the change of the morphologies of solid-liquid interface. The relationship between the character length and the geometrical conditions, the boundary condition and physical properties of the reinforcement were studied, respectively. The results show that the width of the unit and the cold boundary temperature have no effect on the character lengths but have effect on the distance between cold boundary and reinforcement （/） and the thermal parameters of the reinforcement. An experimental rule to predict the value of the character length was derived and applied.     

Microstructure evolution during preparation of in-situ TiB reinforced titanium matrix composites

1　INTRODUCTIONTitaniummatrixcompositesarepromisingmate rialswhichcanbeusedextensivelyinaerospaceandautomotiveindustriesbecauseoftheirexcellentme chanicalpropertiesatroomtemperatureandelevatedtemperature[14 ] ,suchaslowdensity ,highstrength ,andcorrosion resistance .Amongthein situfabrica tionmethodsoftitaniummatrixcomposites[511] ,self propagatinghigh temperaturesynthesis (SHS )methodhasuniqueadvantage ,thatis ,thereinforce mentsarefineanddispersed .InSHS ,thereisanexothermicreactionac…     

Cavitation-erosion mechanism of laser cladded SiC particle reinforced metal matrix composite

With 2 kW continuous wave Nd YAG laser, SiC ceramic powder was laser-cladded on the AA6061 alurniniurn alloy surface. Within the range of process parameters investigated, the parameters were optimized to produce the SiCk, reinforced metal matrix composites(MMC) modified layer on AA6061 alloy surface. After being treated, the modified layer is crack free, porosity-free, and has good metallurgical bond with the substrate. The microstructure and chemical composition of the modified layer were analyzed by such detection devices as scanning electronic microscope(SEM EDX) and X ray diffractometer(XRD). The performance of electrochemical corrosion and cavitation erosion and their mechanism were estimated by the microhardness tester, potentiostat and ultrasonicinduced cavitation device.     

Preparation and properties of Cu matrix composite reinforced by carbon nanotubes

Cu matrix composites reinforced by carbon nanotubes(CNTs) were prepared. The effect of carbon nanotubes on mechanical and tribological properties of the Cu matrix composites were investigated. The chemical method for coating CNTs was reported. The morphology of the fracture surfaces and worn surface were examined by SEM.The results show that Cu/coated-CNTs composites have higher hardness, much better wear resistance and antifriction properties than those of the reference Cu alloy (Cu-10Sn) and Cu/uncoated-CNTs composite sintered under the same conditions. The optimal mechanical properties of the composites occurred at 2. 25%(mass fraction) of CNTs. The excellent wear resistance and anti-friction properties are attributed to the fiber strengthening effect of CNTs and the effect of the spherical wear debris containing carbon nanotubes on the tribo-surface.     

Phase transformation and properties of quasicrystal particles/Al matrix composites

1　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｆｏｒｍａｔｉｏｎｓ,ａｔｏｍｉｃｓｔｒｕｃｔｕｒｅｓ,ｅｌｅｃｔｒｏｎｉｃｓｔｒｕｃｔｕｒｅｓ,ｈｉｇｈｔｅｍｐｅｒａｔｕｒｅｓｔａｂｉｌｉｔｙ,ｐｈａｓｅｔｒａｎｓｆｏｒｍａｔｉｏｎｓａｎｄｐｈｙｓｉｃａｌｐｒｏｐｅｒｔｉｅｓｏｆｑｕａｓｉｃｒｙｓｔａｌｓｈａｖｅｂｅｅｎｓｔｕｄｉｅｄｄｅｅｐｌｙｆｏｒｔｈｅｌａｓｔｔｗｅｌｖｅｙｅａｒｓ,ｂｕｔｉｔｉｓｎｅａｒｌｙｉｍｐｏｓｓｉｂｌｅｔｏｕｓｅｔｈｅｍａｓｆｕｎｄａｍｅｎｔａｌｓｔｒｕｃｔｕｒａｌｍａｔｅｒｉａｌ…     

Non-destructive testing of barely visible impact damage in polymer matrix composites

Barely visible impact damage (BVID) is developed when polymer matrix composites are subjected to impact loading. The damage has an adverse effect on structural integrity, and potentially leads to catastrophic failure.Thus it is important to employ a variety of advanced non-destructive testing (NDT) techniques in parallel to unambiguously determine the integrity of composite systems. This study deals with damage evaluation using visual inspection, ultrasonic C-scan, electronic speckle pattern interferometry (ESPI), electronic shearography (ES) and optical deformation and strain measurement system (ODSMS). Internal damage was introduced using an instrumented falling weight impact test (IFWIT) machine by controlling the combination of striker mass and releasing height. It was found that different NDT techniques were successfully employed to identify and visualise the impact induced internal damage. Experimental results generated from these techniques show a good agreement in damage identification and determination. The features, capabilities and limitations associated with these techniques were briefly discussed.     

Preparation of carbon nanotube composite material with metal matrix by electroplating

It is demonstrated that the nickel can be deposited directly on the surface of carbon nanotubes without pre-sensitization by Sn^2＋ and Pd^2＋ in a watt bath containing suspended nanotubes by electroplating. The nickel is deposited as spherical nanoparticle on the nanotubes. By increasing reaction time, the carbon nanotube is fully coated with nickel. A probable model, which represents the formation process of carbon nanotube-nickel composites by electroplating, is presented. The results show that this method is efficient and simple for preparing carbon nanotube-metal composite.