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℃.

Comparative Assessment on Microstructure and Properties of in-situ TiC+Ti_(5)Si_(3)Reinforced TiAl-Sn-Zr Matrix Composites by Spark Plasma Sintering and Argon Protected Sintering

The effects of SiC particles(SiCp)on high temperature oxidation behavior of titanium matrix composites(TMCs)under different powder metallurgy processes were investigated.In situ Ti C+Ti_(5)Si_(3)reinforced titanium matrix composites were prepared by discharge plasma sintering(SPS)and argon protective sintering(APS).The results show that the two processes have a negligible effect on the composition and hardness of the samples,but the hardness of the two samples is significantly improved by adding SiCp.The apparent porosity of SPS process is obviously smaller than that of APS process,whereas,the apparent porosity increases slightly with the addition of SiCp.The oxide layer thickness and mass gain of the samples obtained by SPS process are smaller than those obtained by APS process.The oxide thickness and mass gain of both processes are further reduced by adding SiCp.The SPS composites showed the best high temperature oxidation resistance.Therefore,TMCs with Si Cp by SPS can effectively improve the high-temperature oxidation behavior of the materials.

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

By means of DTA, SHS quenching, XRD and SEM, the microstructure evolution during fabricating of TiB reinforced in situ titanium matrix composite was studied. DTA result shows that there are two exothermic and one endothermic reaction during heating of Ti B Al system. The exothermic reactions correspond to the solid solid diffusion reaction between Ti and Al, and the reaction of TiB formation respectively, and the endothermic reaction corresponds to melting of Al. The sample of SHS quenching presents four regions: unreacted region, heat affected region, reacting region and product region. The microstructures of these regions reflect the process of microstructure evolution during preparation of in situ TiB reinforced TMC. Ti, B, Al powders are in simple mechanical contact in the unreacted region; the sharp angles of original metal particles have become round and B diffuses into melted Al in the heat affected region; TiB whiskers begin to appear and grow in the interior of reacting region. In product region, the TiB whiskers are uniform and fine. The result of XRD indicates that the reinforcements formed in product region are TiB whiskers. And the TiB is a hexagonal prism with a pyramidal head.

Characterization of In-situ Titanium Matrix Composites Prepared by Laser Melting Deposition

Preliminary characterization of microstructure and mechanical properties of (TiB+TiC)/TC4 and TiC/Ti60 in-situ titanium matrix composites prepared by laser melting deposition is reported in this paper. The results indicate that in-situ reaction occurred during laser melting deposition of coaxially fed mixed powders from TC4 and B4C with formation of form TiB and TiC reinforcement. For TiC/Ti60 composites, there are some un-melted TiC particles and re-solidified TiC particles appeared as discontinuous chain-like morphology. Reinforcements of TiB and TiC with fraction about 25 vol% were formed with feeding 5 wt% B4C. The morphology of TiB tended to be needle-like and prismatic, while TiC appeared as granular. Small amount of un-reacted B4C with reduced size remained within the composites. A thin skull of reaction product formed around the un-reacted B4C weakened its interface bonding with the titanium alloy matrix, thus resulting in less outstanding properties of the composites. Under 600 ℃, the ultimate tensile strength of the TiCP (5wt%)/Ti60 composites was 60 MPa higher than that of Ti60 alloy, following with decreased elongation.

Effect of heat treatment on microstructure,mechanical and tribological properties of in-situ (TiC+TiB)/TC4 composites by casting

To enhance the performance of in-situ synthesized 6vol.%(Ti C+Ti B)/TC4 titanium matrix composites fabricated by casting,a variety of heat treatment processes were carried out.Upon conducting microstructure observations following various heat treatments,it was found that the composites exhibit a basketweave microstructure,consisting of an α phase and a transformed β phase.The sizes of(α+β) phases were found to be refined to varying degrees after the heat treatment processes,while the morphology of Ti B remains largely unchanged and Ti C becomes granulated.Compressive testing revealed that all composites subjected to different heat treatments demonstrate a notable increase in ultimate compressive strength as well as a slight improvement in plasticity compared to the as-cast state.The results of the tribological performance test indicated that the heat-treated composites exhibit lower average friction coefficient,specific wear rate,and worn surface roughness compared to the as-cast composite.Among the heat treatment processes studied,the composite solution heated at 1,150 °C/1 h followed by air cooling,then 950 °C/1 h followed by air cooling,and finally 500 °C/4 h followed by air cooling,demonstrates the highest levels of hardness,compressive strength,and wear resistance.These improvements are attributed to the combined effects of solid solution strengthening,grain refinement,and the pinning of dislocation slip.

Microstructure and formation mechanism of titanium matrix composites coating on Ti-6Al-4V by laser cladding

Laser cladding experiments were done on a 5-kW continuous wave CO2 laser to synthesize TiC and TiB rein- fowed titanium matrix composite coatings on Ti-6AI-4V alloy with a mixture of Ti and B4C precursor powder. The ther- modynamics of the reactions were calculated and analyzed. The microstructure and phase evolution of TiB and TiC com- posites were investigated. The results showed that the chemical reaction between Ti and B4C would release much heat, and these compounds, TiC, TiB, and small amount of TiB2, can be formed on the surface of Ti-6AI-4V alloy if the supplied en- ergy is sufficient to excite the reaction among the initial products. A good metallurgical bond between the coating and the substrate can be achieved. The microhardness of coating was irregular and the maximum value was approximately HV600.

Microstructure and thermal properties of copper matrix composites reinforced with titanium-coated graphite fibers

Milled form of mesophase pitch-based graphite fibers were coated with a titanium layer using chemical vapor deposition technique and Ti-coated graphite fiber/Cu composites were fabricated by hot-pressing sintering. The composites were characterized with X-ray diffraction, scanning/transmission electron microscopies, and by mea- suring thermal properties, including thermal conductivity and coefficient of thermal expansion （CTE）. The results show that the milled fibers are preferentially oriented in a plane perpendicular to the pressing direction, leading to anisotropic thermal properties of the composites. The Ti coating reacted with graphite fiber and formed a continuous and uniform TiC layer. This carbide layer establishes a good metallurgical interracial bonding in the composites, which can improve the thermal properties effectively. When the fiber content ranges from 35 vol% to 50 vol%, the in-plane thermal conductivities of the composites increase from 383 to 407 W.（m.K）-~, and the in-plane CTEs decrease from 9.5 x 10-6 to 6.3 10-6 K-1.

In-situ fabrication of particulate reinforced aluminum matrix composites under high-frequency pulsed electromagnetic field

Pulsed magnetic field is generated when imposing pulse signal on high-frequency magnetic field. Distribution of the inner magnetic intensity in induction coils tends to be uniform. Furthermore oscillation and disturbance phenomena appear in the melt. In. situ Al2O3 and Al3Zr particulate reinforced aluminum matrix composites have been synthesized by direct melt reaction using AlZr（CO3）2 components under a foreign field. The size of reinforced particulates is 2-3 μm. They are well distributed in the matrix. Thermodynamic and kinetic analysis show that high-frequency pulsed magnetic field accelerates heat and mass transfer processes and improves the kinetic condition of in-situ fabrication.

Manufacturing Titanium Metal Matrix Composites by Consolidating Matrix Coated Fibres

Titanium metal matrix composites （TiMMCs） reinforced by continuous silicon carbide fibres are being developed for aerospace applications. TiMMCs manufactured by the consolidation of matrix-coated fibre （MCF） method offer optimum properties because of the resulting uniform fibre distribution, minimum fibre damage and fibre volume fraction control. In this paper, the consolidation of Ti-6Al-4V matrix-coated SiC fibres during vacuum hot pressing has been investigated. Experiments were carried out on multi-ply MCFs under vacuum hot pressing （VHP）. In contrast to most of existing studies, the fibre, arrangement has been carefully controlled either in square or hexagonal arrays throughout the consolidated sample. This has enabled the dynamic consolidation behaviour of MCFs to be demonstrated by eliminating the fibre re-arrangement during the VHP process. The microstructural evolution of the matrix coating was reported and the deformation mechanisms involved were discussed.

Research on development of in situ titanium matrix composites and in situ reaction thermodynamics of the reaction systems

The in situ synthesis method for titanium matrix composites （TMCs） has obvious technical and economical advantages over other traditional methods. Ultrafine reinforcement particles were formed in situ by chemical reaction between elements or between elements and compounds. Using the approach, contamination at the composite matrix/reinforcement particle interface did not occur, interface bonding was good, and the reinforcement particle was thermodynamically stable. The stage of development of the preparation process for in situ TMCs as well as the thermodynamic analysis of the possible in situ reaction systems was described.

Characterization of ceramic reinforced titanium matrix composites fabricated by spark plasma sintering for anti-ballistic applications

Titanium has found extensive use in various engineering applications due to its attractive physical,mechanical, and chemical characteristics. However, titanium has relatively low hardness for use as an armour material. ZrB2 was incorporated to the Ti matrix to form a Ti-based binary composites. In this study, powder metallurgy techniques were employed to disperse the ceramic particulates throughout the matrix material then consolidated through spark plasma sintering. The composites were densified at1300 ℃, pressure of 50 MPa, and holding time of 5 min. The microstructure and phase analysis of the sintered composites was carried out using SEM and XRD, while the hardness was determined using Vickers' microhardness tester. The SEM and XRD results confirmed the presence of the TiB whiskers which renowned with the improving the hardness of titanium. The hardness of the composite with 10 wt% ZrB_2 showed the highest hardness compared to that obtained for the 5 and 15 wt% ZrB_2 composites which was 495 and 571 Hv respectively.

Microstructure and dry sliding wear behavior of as-cast TiCp/Ti-1100-0.5Nb titanium matrix composite at elevated temperatures

The microstructure and dry sliding wear performance of as-cast TiCp/Ti-1100-0.5Nb composite at 25℃,500℃ and 600℃ were systematically investigated.Results show that the solidification matrix microstructure is the typical Widmanst?tten structure.The eutectic TiC particles are uniformly distributed in the matrix in the form of feathery,long rod and strip-like shapes.Meanwhile,the interface between TiC and titanium matrix is clear and without any reaction.The wear rate of TiCp/Ti-1100-0.5Nb at 600℃ and 500℃ is reduced by 95.8%and 79.9%,respectively,compared with that of the value of 51.8×10^-6 mm^3·mm^-1 at 25℃.The friction coefficient of the steady-state period at 25℃,500℃,600℃ is 0.48,0.8,1.2,respectively,and the variation extent of the friction coefficient at elevated temperatures is greater than at 25℃.The wear mechanism is changed from the mixture of adhesive wear and abrasive wear to mild oxidation wear with rising temperature.It can also be concluded that the composite possesses excellent high temperature wear resistance.The high-wear resistance of the composite is attributed to the Fe2O3 and TiO2.The presence of Fe2O3 and TiO2 reduces the wear rate,increases the friction coefficient,and also improves the range-ability of the friction coefficient.

<ji>In Situ</i>Synthesis of Titanium Matrix Composite (Ti-TiB-TiC) through Sintering of TiH₂-B₄C

Fully densified in-situ reinforced (TiB + TiC)-Ti matrix composites have been produced from TiH2-B4C mixtures using pressure less sintering or hot pressing technique. With increasing content of reinforcing components the sintering is retarded. The materials with more than 20 - 30 vol. % were only completely densified by hot pressing technique. Hardness values of the Ti matrix composites produced are up to 5 times higher than that of the sintered pure Ti produced from TiH2. This is caused beside the higher hardness of the inclusions also by hardening the matrix due to solubility of B and C in the titanium.

Microstructure and properties of submicron-scale TiC particle reinforced titanium matrix composites prepared by shock wave consolidation

Submicron-scale TiC particle reinforced titanium matrix composites(TMCs) were prepared by shock wave consolidation technique at detonation speed of 2 5005 000 m/s. The microstructures were studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The compressive strength and hardness values of the composites were also determined. The results show that the composites have higher compressive yield strength and hardness values than hot-rolled pure titanium. Twins in the microstructure of TMCs show that titanium particles undergo plastic deformation during consolidation process. The fine grains with size less than 1 μm often locate in the boundaries among the titanium particles. TiC particles seem to keep unchanged during the consolidation. These bring about the increase in strength and hardness for the composites. The detonation speed of 3 200 m/s is proper parameter for compacting powder in the present work.

Finite Element Analysis of Push-Out Test of SiC Fiber Reinforced Titanium Matrix Composites

Based on the interphase layer model and the spring layer model, an improved interface model was developed to evaluate the interfacial shear strength of Titanium matrix composites(TMCs) and to analyze the effects of various parameters on the interfacial properties. The results showed that the improved interface model is more suitable for calculating the interfacial properties of SiC fiber reinforced titanium matrix composites. The interfacial shear strength of SiC/Timetal-834 predicted is 500 MPa. In addition, in order to better understand the interfacial properties of composites, some push out phenomenon were analyzed.

Milling Machinability of TiC Particle and TiB Whisker Hybrid Reinforced Titanium Matrix Composites

The milling machinabilities of titanium matrix composites were comprehensively evaluated to provide a theoretical basis for cutting parameter determination.Polycrystalline diamond(PCD)tools with different grain sizes and geometries,and carbide tools with and without coatings were used in the experiments.Milling forces,milling temperatures,tool lifetimes,tool wear,and machined surface integrities were investigated.The PCD tool required a primary cutting force 15%smaller than that of the carbide tool,while the uncoated carbide tool required a primary cutting force 10% higher than that of the TiAlN-coated tool.A cutting force of 300 Nper millimeter of the cutting edge(300N/mm)was measured.This caused excessive tool chipping.The cutting temperature of the PCD tool was 20%—30%lower than that of the carbide tool,while that of the TiAlN-coated tool was 12%lower than that of the uncoated carbide tool.The cutting temperatures produced when using water-based cooling and minimal quantity lubrication(MQL)were reduced by 100°C and 200°C,compared with those recorded with dry cutting,respectively.In general,the PCD tool lifetimes were 2—3 times longer than the carbide tool lifetimes.The roughness Raof the machined surface was less than 0.6μm,and the depth of the machined surface hardened layer was in the range of 0.15—0.25 mm for all of the PCD tools before a flank wear land of 0.2mm was reached.The PCD tool with a 0.8mm tool nose radius,0°rake angle,10°flank angle,and grain size of(30+2)μm exhibited the best cutting performance.For this specific tool,a lifetime of 16 min can be expected.

Evaluation the Properties of Titanium Matrix Composites by Melting Route Synthesis

The main purpose of this study is an in-situ synthesis of （TiB＋TiC） hybrid titanium matrix composites （TMCs） by vacuum induction melting method and to verify its mechanical properties.The melting route was adopted to synthesize the commercial pure titanium （cp Ti） and granular boron carbide （B-4C）.The reinforcements,the fraction of 10 vol.pct,were formed by adding 1.88 wt pct B-4C to cp Ti.After in-situ synthesis of TMCs,electron probe micro-analysis elemental mapping was carried out to confirm the distribution and shape of reinforcements.The cone-on-disk type sliding wear test was also done for the identification of TMCs.It is concluded that （TiB＋TiC） hybrid TMCs can be in-situ synthesized and has better wear properties than H13.

Microstructure of in situ TiC particle reinforced titanium alloy matrix composites

TiC particle reinforced titanium alloy matrix composites with different aluminum content was prepared by the XD TM method. The constitute phase and the microstructure of the composites were studied by XRD and SEM. The results show that the calculated lattice parameter of TiC there exists a diffraction peak shift for TiC, which may be due to the vacancies of C in TiC. The stoichiometry of TiC is Ti 62 C 38 . There exist two different kinds of TiC in the composites: dendritic primary TiC and short bar shape eutectic TiC, respectively. Although TiC of macrostructure is homogeneously distributed in the matrix, the eutectic TiC of microstructure mainly segregates at the grain boundary, especially at the triangular grain boundaries. The aluminum content has a great influence on the morphology of TiC. With increasing aluminum content up to 25%, the size of TiC becomes small although it is still in dendrite or short bar shape. When the aluminum content is more than 35%, TiC is changed into thin plate or particle and the size is about 2～5 μm. [

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.

FATIGUE CRACK GROWTH FEATURE OF Fe-Cr-Ni MATRIX COMPOSITE REINFORCED BY TITANIUM CARBIDE PARTICULATE AT 1023K

The initiation and propagation of the short fatigue crack in a 10vol% titanium carbide particulate reichreed cast Fe-26Cr-14Ni mathe coopsite at 1023K were investigated.It is shown that the titanium carbide particulate may hinder the crack propagation and fatigue fracture of the composite. The relationships between fatigue crack propagation rate and stress intensity factor are da/dN=4.2×10-c(△K)4 for the matrix alloy and da/dN=1.4×10-19(△K)c for the composite. The fatigue thresholds of the composite and mathe alloy are 78 and 3.2MPa.m1/2, respectively. Microcracks initiate at the intedece between titanium carbide particulate and austenite and then propagate in carkide particles. The fracture sudece of the composite shows a distinct transition from wavy and serated cleavage near the threshold regime to striation-type splitting in the stable fatigue crack propagation stage and to a veined morphology characteristic in unstable rapid region.