Effect of Cerium on Microstructures and High Temperature Oxidation Resistance of An Nb-Si System In-Situ Composite

Nb-16Si-24Ti-6Cr-6A1-2Hf-xCe （x =0, 0.05, 0.1,02.5, 0.5, 1 （%, atom fraction）） in situ composites were prepared by arc melting The microstmcture and the effect of rare earth element cerium on 1250℃ oxidation resistance of the composites were investigated with scanning electron microscopy （SEM） and X-ray energy disperse spectrum （EDS）, as well as X-ray diffraction （XRD）. The experimental results showed that the high temperature oxidation resistance of the alloy was improved by adding a proper amount of cerium （Ce）. The effect of Ce was considered as the concurrent of the following three factors： first, the oxide of Ce formed in the interface reduced the internal oxidation rate; second, the lath shaped oxide containing Ce increased the cracking resistance and reduced the expansion of the oxide scale; and third, the decrease of the sificide volume fraction on account of Ce addition reduces the power of the sample resisting oxygen penetration.

In-situ Composite Based on Poly (ethylene terephthalate),Polyamide and Polyethylene with Microfibres Formed through Extrusion and Hot Stretching

In-situ composites based on dispersed poly (ethylene terephthalate) (PET) or polyamide (PA), and continuous polyethylene (PE) were prepared through a single screw extruder of Haake rheometer system with a rod-die relatively small in diameter. The extrudate was drawn at a drawing ratio of 3.1, and then quickly cooled in cold water. The specimens were obtained by injection molding at processing temperatures less than 190℃, far below the melting temperature of PET (265℃) and PA (230℃), which can maintain the solid state of PET and PA microfiber phase in the composites. Morphological observation with scanning electron microscopy (SEM) indicated that PET and PA can more or less form in-situ microfibers at compositions studied (0~20 wt pct PET or PA), and especially, PET and PA were almost deformed into fibers at the concentration of 15 wt pct. Tensile strength and modulus of the blends reinforced by PET or PA microfibers showed to be increased from the tensile test results. The most noticeable improvement of the tensile properties occurred at 15 wt pct of PET in PET/PE system, corresponding to the highest microfiber content, where the tensile strength reached 32.5 MPa, whereas only 19.5 MPa for the pure PE.

In-situ composite Cu-Cr contact cables with high strength and high conductivity

In order to develop a new type of contact cable with high strengthand high electrical conductivity, Cu-Cr alloy series were selected asmaterials and cu-Cr alloy castings were produced by means ofdirectional solidification continu- ous casting (DSCC) process. theresults show that the fibrillar strengthening phase, β-Cr, orderlyarranges among the copper matrix phase along the wire direction; andmicrostructure of in-situ composite forms, which retains the basicproperty of good conductivity of the copper matrix and meanwhileobtains the strengthening effect ofβ-Cr phase.

FILLED POLYOLEFIN COMPOSITES PREPARED FROM IN-SITU POLYMERIZATION VIA A CATALYST-SUPPORTED APPROACH——Ⅰ.MORPHOLOGY OF PE IN CARBON BLACK(CB)/PE IN-SITU COMPOSITES

The morphology of PE in the in-situ CB/PE composites prepared from in-situ polymerization via a catalyst-supported approach was studied by DSC. It is found that both the melting peak temperature and crystallinity of the PE shelldecrease as filler level increases. The unexpected phenomena are ascribed to the strong interaction between PE and CB andthe very high specific area of CB. It is suggested that the lamellar thickness should be well correlated to the PE shell thickness. A two-layer PE model is successfully used to explain the experiment results.

STRUCTURES AND PROPERTIES IN IN-SITU COMPOSITES ITES OF LC70/PET

Structures and properties of the blends of thermotropic liquid crystallinepolymer(LC70)and poly(ethylene terephthalate) (PET) were investigated by usingWAXD,DSC,SEM and mechanical test.The results revealed that Wc,x markdly decreased withLC70/PET>30%,and at about LC70/PET=10%, this blend can yield better mechanicalproperties.In these blends LC70 can play the role of the nuclear agent for PET.SEMphoto showed that LC70/PET in in-situ composites possessed 'core-shell' structure andwas immiscible, but at LC70/PST=10%, the LC70 can be uniformly dispersed into matrix PET.

Microstructure Evolution and Thermal Stability of Cu-15Cr in-situ Composites

The Cu-15Cr in-situ fiber-reinforced composites sheets were prepared by cold drawing combined with cold rolling process. The evolution process of Cr fibers was studied, and when cold rolling reduction ε = 95%, the morphology of Cr fiber at different annealing temperature and the thermal stability of Cu-15Cr alloy were studied. Microstructure was also studied by scanning electron microscopy（SEM）. Meanwhile, the tensile strength of the alloy was tested by means of a precision universal tester, and the resistance value of the alloy was determined by using a digital micro-Euclidean instrument. The experimental results show that, with the increase of deformation, Cr dendrites evolve into homogeneous and parallelly arranged Cr fibers, and the cross-section of Cr fibers undergoes a ＂V＂ shape transition to ＂一＂ shape. In addition, spheroidization of the Cr fibers occurs on edges and extends to the center as annealing temperature rises. Moreover, the Cr fibers remains stable when the annealing temperature is below 550 ℃. Furthermore, the tensile strength of Cu-15Cr alloy decreases gradually as the annealing temperature increases, while the electrical conductivity maximizes when annealing at 550 ℃. Our study also shows that Cu-15Cr alloy has obtained a better comprehensive performance with tensile strength of 656 MPa and electrical conductivity of 82%IACS after annealing at 450 ℃.

Influence of Friction Stir Welding Parameters on Sliding Wear Behavior of AA6061/0-10 wt.% ZrB₂in-situ Composite Butt Joints

Over the last decade attempts have been made to fabricate aluminum matrix composites (AMCs) reinforced with several ceramic particles. Aluminum reinforced with ZrB2 particles is one such AMC. The successful application of new kind of AMCs lies in the development of secondary processes such as machining and joining. Friction stir welding (FSW) is a relatively new solid state welding which overcomes all the setbacks of fusion welding of AMCs. An attempt has been made to friction stir weld AA6061/ 0-10 wt. % ZrB2 in-situ composites and to develop empirical relationships to predict the sliding wear behavior of butt joints. Four factors, five levels central composite rotatable design has been used to minimize the number of experiments. The factors considered are tool rotational speed, welding speed, axial force and weight percentage of ZrB2. The effect of these factors on wear rate (W) and wear resistance (R) of the welded joints is analyzed and the predicted trends are discussed.

Corrosion Behaviour of TiC-Reinforced Hadfield Manganese Austenitic Steel Matrix In-Situ Composites

The corrosion behaviour of Hadfield manganese austenitic steel matrix composite reinforced with the varying amount of TiC and unreinforced Hadfield manganese austenitic steel matrix alloy has been evaluated in 3.5% NaCl aqueous solution with the pH value of 6 by the potentiodynamic polarization curves and linear polarization resistance measurements at a scan rate of 1 mV/s at room temperature (25°C ± 2°C). The corrosion rate of the composites is higher than that of their unreinforced matrix alloy and it increases with the increasing volume fraction of TiC. The poor corrosion resistance of the composites can be attributed to the galvanic effects between the matrix and reinforcement.

Evolution of TaC morphology during directional solidification of Ni, Cr, Al-TaC in-situ composite

The Ni, Cr, Al-TaC composite was directionally cast from a nickel-base alloy with a nominal mass composition of Ni-10Cr-5.0Al-13.9Ta-0.9C (mass fraction, %). The morphologies of TaC in the in-situ composite was observed with AMRAY100B SEM. TEM investigations were preformed in a JEM2000CX instrument at 150kV. The experimental results show that TaC fibers are grown from the dendritic arms of the primary blocky TaC in the bottom of the directionally solidified Ni, Cr, Al-TaC sample. The longitudinal growth of TaC fibers is controlled by the pyramid growth mechanism under forced heat flow of [001] orientation. The transverse growth pattern of TaC is markedly affected by the unstable mode. The multiplicity of TaC transverse morphologies is presented.

Sb-Mn Alloy in-situ Composites and Magnetic Properties

The microstructures and magnetic properties of two in-situ composites, directionally solidified Sb-9.5%Mn and Sb-50%Mn alloys, were investigated. The aligned ferromagnetic compound MuSb or Mn2Sb was embedded in Sb or Mn matrix with varying Mn content. The magnetization curves and thermal magnetic Curves were examined along solidification direction, which reveals the magnetic behaviors of the composites.

Microstructure of Nb/Nb_5Si_3 in-situ composites

The Nb 10Si (mole fraction, %) alloy was fabricated using the vacuum arc melting method and heat treated at 1850?℃ and 1?550?℃ for 2～100?h in Ar atmosphere. The microstructure of the alloy has been investigated using X ray diffractometry(XRD), scanning electron microscopy (SEM) equipped with X ray energy dispersive spectrometry (EDS) and transmission electron microscopy (TEM). The results show that 1?550?℃, 100?h is an optimum heat treatment condition to acquire the equilibrium Nb+Nb 5Si 3 two phase microstructure. The microstructure of Nb 10Si alloy in the as cast condition consists of continuous Nb 3Si matrix and dispersed Nb particles, which implies that the alloy is in the metastable equilibrium state. In the case of 1?850?℃, 2?h heat treatment the Nb particles are coarsened evidently. However, in the heat treatment condition of 1?550?℃ for 25～100?h the growth of Nb particles is unconspicuous. After heat treated at 1?550?℃, Nb 3Si phase transforms into the equilibrium Nb 5Si 3 and Nb phase with the increase of heat treatment time gradually. TEM observations reveal that the interface of Nb phase and Nb 5Si 3 phase is clean and some twins with about 10?nm in width are found.

Effect of alloying elements on mechanical properties in Cu-15%Cr in-situ composites

The effects of alloying elements on the mechanical properties as well as electrical conductivity in Cu-15%Cr(mass fraction) in-situ composites were systematically studied and high strength and high electrical conductive Cu base in-situ composites have been developed. The best combination is the addition of 0.1% to 0.2% Zr, Ti, or Sn in Cu-15%Cr in-situ composite, thermomechanical treatment to refine the microstructure and optimizing the precipitation of second phase. The strength is controlled by high density of dislocations in the Cu matrix, the lamellar spacing of the second phase, and the fine Cr precipitates. The aging treatment to reduce solute atoms has a beneficial effect on the increase of electrical conductivity. The addition of Zr, or Ti of about 0.15% to 0.2% promotes the precipitation of Cr particles.

Effects of V and Al on Microstructure and Room Temperature Fracture Toughness of Nb-Si In-situ Composites

The effect of alloying elements V and Al on microstructure and room temperature fracture toughness of an experimental Nb-Si in-situ composite was investigated. The Nb-Si alloys with different amount of V and Al were prepared by non-consumable arc-melting furnace. The experimental results showed that with the addition of V and Al, the microstructure of the Nb-Si materials transformed from Nbss+Nb3Si to Nbss+Nb5Si3 and the lattice parameters of Nbss phase decreased, and the alloying element V promoted the formation of the finer Nbss structure. It was observed that the room temperature fracture toughness was improved by the addition of V and Al, and the optimum room-temperature fracture toughness of the material appeared in the alloy with 2.6at.%V and 3.6at.%Al. The improvement of room temperature fracture toughness may be mainly attributed to the increment of the volume fraction of Nbss phase and the decrement of the silicide phase size.

Structures and properties of deformation-processed Cu-16Fe-2Cr in-situ composites

Microstructure and properties of deformation processed Cu 16Fe 2Cr and Cu 18Fe in situ composite wires obtained by cold drawing combined with intermediate annealing were investigated. At lower strains( η <2.52), most of the Fe(Cr) phases were elongated into filaments except some remain granular because of their higher hardness. The ultimate tensile strengths of Cu 16Fe 2Cr and Cu 18Fe are approximately equal at the same drawing strains, suggesting the increase of strength of Cu 16Fe 2Cr due to higher strength of Fe(Cr) filaments than that of Fe filaments which is counteracted by the somewhat coarse Fe(Cr) filaments in Cu 16Fe 2Cr at the same drawing strains. The increase of the electrical conductivity of Cu 16Fe 2Cr and Cu 18Fe after intermediate annealing is attributed to the precipitation of Fe, Cr atoms, which dissolved during melting processing. Electrical conductivity of the Cu 16Fe 2Cr in situ composites is higher than Cu 18Fe in situ composites at the same drawing strains. The addition of Cr to Cu Fe system can increase mechanical stability of the filaments in the composites.

Strength of deformation-processed Cu-Fe in-situ composites

The strength of the deformation-processed Cu-Fe in-situ composite was conducted by material test system(MTS). The results show that the strength increases with the increasing deformation strain and iron content,which is greater than that of the calculated value based on the rule of mixture. The mechanism of strengthening was analysed and evidenced by interface barrier. The correlation between the strength and the thickness of copper phase (tcu) obeys Hall-Petch relationship and can be described well by geometrical necessary dislocation model and interface as dislocation source model.

Microstructure and properties of deformation-processed Cu-Fe in-situ composites

The effects of intermediate annealings on the microstructure, the strength and the electrical resistivity of deformation-processed Cu-Fe in-situ composites were studied. The results show that intermediate annealings favour the formation of uniform tiny fibres from the iron dendrites but they have no obvious effect on the strength of the composite. The bigger the strain is, the higher the strength is. As the strain increases, the resistivity increases due to the increase of interface density. Intermediate annealings result in notable decreasing resistivity due to the precipitation of the iron atoms from the Cu matrix and decrease of solute scattering resistivity. The doping with Zr improves the strength of the composite slightly and the ultimate tensile strength(UTS) increases about 10%. The colligated performances of deformation-processed Cu-11.5%Fe and Cu- 11.5%Fe-Zr composites at strain η= 5.37 are 64.6% IACS/752MPa and 61.4% IACS/824MPa respectively.

Microstructural characterization and mechanical properties of(TiC+TiB)/TA15 composites prepared by an in-situ synthesis method

Titanium matrix composites reinforced with ceramic particles are considered a promising engineering material due to their combination of high specific strength,low density,and high modulus.In this study,the TA15-based composites reinforced with a volume fraction of 10% to 25%(TiB+TiC)were prepared using powder metallurgy and casting technique.Microstructural characterization and phase constitution were examined using optical microscopy(OM),scanning electron microscopy(SEM),and X-ray diffraction(XRD).In addition,the microhardness,room temperature(RT)and high temperature(HT)tensile properties of the composites were evaluated.Results revealed that the reinforcements are distributed uniformly even in the composites with a high volume of TiB and TiC.However,as the volume fraction exceeds 15%,TiB and TiC particles become coarsening and exhibit rod-like and dendritic-like morphology.Microhardness increases gradually from 321.2 HV for the base alloy to a maximum of 473.3 HV as the reinforcement increases to 25vol.%.Tensile test results indicate that a reinforcement volume fraction above 20% is beneficial for enhancing tensile strength and yield strength at high temperatures,but it has an adverse effect on room temperature elongation.Conversely,if the reinforcement volume fraction is below 20%,it can improve high-temperature elongation when the temperature exceeds 600℃.

In-situ additive manufacturing of high strength yet ductility titanium composites with gradient layered structure using N_(2)

It has always been challenging work to reconcile the contradiction between the strength and plasticity of titanium materials.Laser powder bed fusion(LPBF) is a convenient method to fabricate innovative composites including those inspired by gradient layered materials.In this work,we used LPBF to selectively prepare Ti N/Ti gradient layered structure(GLSTi)composites by using different N_(2)–Ar ratios during the LPBF process.We systematically investigated the mechanisms of in-situ synthesis Ti N,high strength and ductility of GLSTi composites using microscopic analysis,TEM characterization,and tensile testing with digital image correlation.Besides,a digital correspondence was established between the N_(2) concentration and the volume fraction of LPBF in-situ synthesized Ti N.Our results show that the GLSTi composites exhibit superior mechanical properties compared to pure titanium fabricated by LPBF under pure Ar.Specifically,the tensile strength of GLSTi was more than 1.5times higher than that of LPBF-formed pure titanium,reaching up to 1100 MPa,while maintaining a high elongation at fracture of 17%.GLSTi breaks the bottleneck of high strength but low ductility exhibited by conventional nanoceramic particle-strengthened titanium matrix composites,and the hetero-deformation induced strengthening effect formed by the Ti N/Ti layered structure explained its strength-plasticity balanced principle.The microhardness exhibits a jagged variation of the relatively low hardness of 245 HV0.2 for the pure titanium layer and a high hardness of 408 HV0.2 for the N_(2) in-situ synthesis layer.Our study provides a new concept for the structure-performance digital customization of 3D-printed Ti-based composites.

Investigation into machining performance of microstructurally engineered in-situ particle reinforced magnesium matrix composite

Magnesium and magnesium in-situ composites have significant potential in the application of design and manufacturing for automotive and aerospace industries because of their high specific strength and reduced fuel consumption.But there are many challenges for machining of Mg based alloys and composites because of the high tendency of fire and oxidation.These challenges can be minimized through microstructural engineering.In this present study,the machining performances of AZ91 Mg alloy and in-situ hybrid TiC+TiB_(2)reinforced AZ91 metal matrix composite was investigated.The effectβ-Mg_(17)Al_(12)phases and grain refinement with and without in-situ particles on machinability were studied through microstructural engineering via aging and friction stir processing.The end milling operation was carried out at different cutting speeds ranging from 25 mm/min to 90 mm/min under dry environment by using an AlTiN-coated tungsten carbide tool.The optimum cutting speed for machining was found to be 75 mm/min based on the surface roughness values of all conditioned materials.The base material with dendritic microstructure was found to have poor machinability in terms of inadequate surface finish and edge-burrs formation.The combined effect of in-situ TiC+TiB_(2)particles addition and grain refinement enhanced the machining performance of the material with superior surface finish,negligible edge-burr formation and better tool wear resistance.The influence of in-situ TiC+TiB_(2)particles,β-Mg_(17)Al_(12)phases and grain refinement on machining characteristics are explained based on the tool wear mechanisms,chip behavior and machining induced affected zone.

In-situ deposition of apatite layer to protect Mg-based composite fabricated via laser additive manufacturing

Biodegradable magnesium(Mg) and its alloy show huge potential as temporary bone substitute due to the favorable biocompatibility and mechanical compatibility. However, one issue deserves attention is the too fast degradation. In this work, mesoporous bioglass(MBG)with high pore volume(0.59 cc/g) and huge specific surface area(110.78 m^(2)/g) was synthesized using improved sol-gel method, and introduced into Mg-based composite via laser additive manufacturing. Immersion tests showed that the incorporated MBG served as powerful adsorption sites, which promoted the in-situ deposition of apatite by successively adsorbing Ca2+and HPO42-. Such dense apatite film acted as an efficient protection layer and enhanced the corrosion resistance of Mg matrix, which was proved by the electrochemical impedance spectroscopy measurements. Thereby, Mg based composite showed a significantly decreased degradation rate of 0.31 mm/year. Furthermore,MBG also improved the mechanical properties as well as cell behavior. This work highlighted the advantages of MBG in the fabrication of Mg-based implant with enhanced overall performance for orthopedic application.