Comprehensive Study on Machinability of Titanium Composite

Metal framework composites have higher mechanical properties in examination to metals over an extensive variety of working conditions. This makes them an alluring alternative in swapping metals for different building applications. The present review is a study on the influence of composite titanium on the cutting parameters, mechanical behavior, reinforcements, structure and nanostructure. This review will provide an understanding into selecting the optimum machining parameters for machining titanium composites. It’s also an attempt to give brief explanation by suitably machining the titanium composite which can be made reasonable.

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℃.

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.

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.

Mechanical and tribological properties of graphene nanoplatelets-reinforced titanium composites fabricated by powder metallurgy

Titanium matrix composite reinforced by graphene nanoplatelets(GNPs)was fabricated via powder metallurgy route.Hot isostatic pressing and hot extrusion were used to consolidate the mixed powder of GNPs and TC4 titanium(Ti)alloy.The microstructures,mechanical properties and sliding wear performance of Ti/GNPs composite had been researched to evaluate the rein forcing effect of GNPs on tita nium matrix.Microstructure observation indicates that GNPs could restrain grai n growth slightly in titanium matrix.Titanium matrix and graphene exhibit a clean and firm interface formed by means of metallurgical bonding on atomic scale.Compared with the monolithic titanium alloy,the composite with 1.2 vol.%GNPs exhibits significantly improved elastic modulus and strength.The sliding wear test shows that there is an obvious enhancement in the tribological performance of Ti/GNPs composite with 1.2 vol.%GNPs.The results of this work indicate that GNP is an efficient reinforcenient material in titanium matrix.The strengthening mechanism including precipitates strengthening,load transfer and grain refinement mechanism of GNPs in titanium matrix was discussed.A modified shear-lag model was used to analyze the reinforcement contribution of the stress transfer mechanism.The calculation shows that the stress load mechanism constitutes the main strengthening mechanism in Ti/GNPs composite.

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.

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.

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.

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.

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.

Reaction Processes of the Titanium Matrix Composites Fabricated from Ti-Al-B2O3 System

Titanium matrix composites reinforced with a-Al2O3 and TiB2 particles were fabricated by in situ synthesis from a Ti-Al-B2O3 system. The reaction processes and microstructure were analyzed by using differential scanning calorimetry（DSC）, scanning electron microscopy（SEM） and X-ray diffraction（XRD）. The results showed that the reactions in the Ti-Al-B2O3 system can occur spontaneously and consist of three steps： 1） 15 Al ＋ 7B2O3 → 7α-Al2O3 ＋ AlB12 ＋ 2B; 2） 14 B ＋ 2Al → AlB12 ＋ AlB2 and 3） 7Ti ＋ AlB（12） ＋ AlB2 → 7TiB2 ＋ 2Al. The final reinforcements were composed of α-Al2O3 and TiB2 particles, which were uniformly distributed in the titanium matrix.

Corrosion and wear properties of in situ(TiB+TiC)/TA15 composites with a high volume percentage of reinforcement

The in situ(TiC+TiB)/TA15 composites with different volume percentages of reinforcement(10%,15%,20%and 25%)were prepared by water-cooled copper crucible vacuum suspension melting technology.The structures and compositions of the TA15 alloy and its composites were analyzed by XRD and EDS,and their electrochemical corrosion behaviors in the 3.5%NaCl solution were studied.Corrosion wear testing was conducted using a reciprocating ball-on-disc wear tester under a 10 N load.Results show that the in situ fibrous TiB phase and the granular TiC phase are uniformly distributed on the composite matrix.The microhardness can reach up to 531 HV as 25vol.%TiC+TiB reinforcement is added.Compared with the TA15 alloy,the volume wear rate decreases from(2.21±0.07)×10^(-4)to(1.75±0.07)×10^(-4)mm^(3)·N^(-1)·m^(-1)by adding 15vol.%TiC+TiB reinforcement,and the wear mechanism is adhesive wear.When the volume percentage of the reinforcement phase reaches 25%,the volume wear rate increases from(1.75±0.07)×10^(-4)to(2.41±0.07)×10^(-4)mm^(3)·N^(-1)·m^(-1),and the wear mechanism changes into abrasive wear.The volume loss resulted by the interaction between corrosion and wear accounts for more than 27%of the total wear volume.The volume loss due to wear-induced corrosion changes from 1.94%to 4.06%with different additions of reinforcement.The volume loss caused by corrosion-induced wear initially increases from 24.08%to 26.90%as the reinforcement increases from 0 to 15%due to the increase of corrosion potential,and then decreases from 26.90%to 25.68%as the reinforcement increases from 15%to 25%due to the peeling of TiC phase.

Mechanical properties and thermal deformation behavior of low-cost titanium matrix composites prepared by a structure-optimized Y_(2)O_(3) crucible

A porous yttrium oxide crucible with both thermal shock resistance and erosion resistance was developed by structural optimization.The structure-optimized yttrium oxide crucible was proved to be suitable for melting highly reactive titanium alloys.Low-cost(TiB+Y2O_(3))-reinforced titanium matrix composites were prepared by vacuum induction melting using the prepared crucible.The thermal deformation behavior and microstructure evolution of(TiB+Y2O_(3))-reinforced tita-nium matrix composites were investigated at deformation temperatures of 900-1100℃with strain rates of 0.001-1 s-1.The results showed that the prepared yttrium oxide crucible had both thermal shock and erosion resistance,the low-cost titanium matrix composites could be prepared by the developed yttrium oxide crucibles which were homogeneous in composition and highly sensitive to strain rate and deformation temperature,and the peak and theological stresses decreased with increasing deformation temperature or decreasing strain rate.In addition,the average thermal deformation activation energy of the composites was calculated to be 574.6 kJ/mol by establishing the Arrhenius constitutive equation in consideration of the strain variables,and the fitting goodness between the predicted stress value and the measured value was 97.624%.The calculated analysis of the hot processing map showed that the best stable thermal deformation zone was located in the deformation temperature range of 1000-1100℃and strain rate range of 0.001-0.01 s^(-1),where the peak dissipation coefficient wasη=71%.In this zone,the deformation of the reinforcement and matrix was harmonious,the reinforcement was less likely to fracture,dynamic recrystallization occurred more fully and the alloy exhibited near steady rheological characteristics.

Reaction procedure of a graphite fiber reinforced Ti-Al composite produced by squeeze casting-in situ reaction

The in situ reaction procedure and microstructure evolution of a graphite fiber reinforced Ti-Al composite （Grf/Ti-Al） was investigated, and the stability of TiAl3 at high temperature was discussed. As-cast material was prepared by pressing molten pure aluminum into a preform, which was composed of titanium particles and graphite fibers. The in situ reaction procedure of the as-cast material was investigated by differential scanning calorimetry （DSC）, and phases in the products were detected by X-ray diffraction （XRD）. Experimental results showed that TiAl3 was formed first. With an increase in temperature, TiC and Al4C3 were observed, but TiAl3 decreased. In the final product, Al2O3 and TiO2 were observed. It was considered that the previous forming TiAl3 decomposed, then TiC precipitated, and subsequently, oxidation resulted in the formation of Al2O3 and TiO2.

Elastic and Plastic Behaviors of Laminated Ti-TiBw/Ti Composites

The novel laminated Ti-TiBw/Ti composites composed of pure Ti layers and TiBw/Ti composite layers have been successfully fabricated by reactive hot pressing. Herein, two-scale structures formed： the pure Ti layer and TiBw/Ti composite layer together constructed a laminated structure at a macro scale. Furthermore, TiBw reinforcement was distributed around Ti particles and then formed a network microstructure in TiBw/Ti composite layer at a micro scale. The laminated Ti-TiBw/Ti composites reveal a superior combination of high strength and high elongation due to two-scale structures compared with the pure Ti, and a further enhancement in ductility compared with the network structured composites. Moreover, the elastic modulus of the laminated composites can be predicted by H-S upper bound, which is consistent with the experimental values.

Effects of MgO and TiO_2 on the viscous behaviors and phase compositions of titanium-bearing slag

The effects of MgO and TiO_2 on the viscosity, activation energy for viscous flow, and break-point temperature of titanium-bearing slag were studied. The correlation between viscosity and slag structure was analyzed by Fourier transform infrared（FTIR） spectroscopy. Subsequently, main phases in the slag and their content changes were investigated by X-ray diffraction and Factsage 6.4 software package. The results show that the viscosity decreases when the MgO content increases from 10.00wt% to 14.00wt%. Moreover, the break-point temperature increases, and the activation energy for viscous flow initially increases and subsequently decreases. In addition, with increasing TiO_2 content from 5.00wt% to 9.00wt%, the viscosity decreases, and the break-point temperature and activation energy for viscous flow initially decrease and subsequently increase. FTIR analyses reveal that the polymerization degree of complex viscous units in titanium-bearing slag decreases with increasing MgO and TiO_2 contents. The mechanism of viscosity variation was elucidated. The basic phase in experimental slags is melilite. Besides, as the MgO content increases, the amount of magnesia–alumina spinel in the slag increases. Similarly, the sum of pyroxene and perovskite phases in the slag increases with increasing TiO_2 content.

Effect of C/Mo Duplex-coating on Thermal Residual Stresses in SiCf/Ti2AlNb Composites

Three-dimensional finite element physical models considering the layered distribution of materials at the interface were developed to study the effect of the coating system on distributions of thermal residual stresses in SiCf/Ti2AlNb composites.Two coating systems were comparatively studied,namely C coating and C/Mo duplex-coating.The thermal residual stresses after 1 080 ℃/1 h solution treatment and 800 ℃/20 h ageing treatment in the composites were also analyzed.The experimental results show that Mo coating can decrease thermal residual stress magnitude in the matrix.However,it would increase the thermal residual stresses in the interfacial reaction layer of TiC.The change of radial thermal residual stress in TiC layer is inconspicuous after solid solution and ageing treatment,but the hoop and axial thermal residual stresses increase obviously.However,the heat treatment can obviously reduce hoop and axial thermal residual stresses of the matrix,which is benefit to restrain the initiation and propagation of cracks in the matrix.

Superplastic behavior of in situ synthesized (TiB+TiC)/Ti matrix composite

The superplastic deformation behavior of titanium alloy matrix composites reinforced with TiB and TiC was studied. Superplastic tension tests under conditions from 750℃ to 1100℃ and initial strain rates ranging from 2×10^-2 s^-1 to 10^-4s^-1 were carried out. A maximum elongation of 659% was obtained. The micro-structural evolution was studied by means of optical microscopy （OM） and transmission electron microcopy （TEM）. The deformation mechanism and the effect of reinforcement on superplasticity are also discussed.

Mechanical Properties and Electrical Conductivity of TiN-Al_2O_3 Composites

TiN- Al2O3 composite powders with different TiN contents （0, 10 vol%, 20 vol%, 30 vol% and 40 vol% ）were prepared with micrometer TiN and α-Al2O3 powder （ their purities were 99% ） as starting materials by wet ball milling for 5 h. TiN-Al2O3 composite were then prepared by pressing the above composite powders, drying at 200 ℃ for 12 h and firing at 1 800 ℃ for 3 h in nitrogen atmosphere in hot-pressing furnace. The influences of TiN content on mechanical properties and electrical conductivity of TiN -Al2O3 composites were studied. The results showed that the mechanical properties of the composite increased with TiN content increasing, while the resistivity of composites decreased. A composite with 40% TiN had 498 MPa ben- ding strength, 4. 285 MPa· m1/2 fracture toughness, 1.34×10^-3 Ω· cm resistivity. The SEM analysis showed that the fine TiN crystals distributed among the crystal boundary of Al2O3 matrix. They bonded together forming a net-like structure which played a role of restraining Al2O3 grains from growing up, toughening and strengthening, so the mechanical properties of TiN -Al2O3 composite were enhanced.

TiN/Al_2O_3 Composite Material Synthesized by Aluminothermic Reduction Process in Coke Bed

TiN/Al2O3 composite material was prepared by aluminothermic reduction of TiO2 in coke bed. The phase composition, lattice parameter and microstructure of products treated at 1 300 ℃ , 1 400 ℃, 1 500℃ for 3 h respectively were analyzed by XRD, SEM and TEM. The results showed that TiN/Al2O3 composite material can be prepared in coke bed via aluminothermic reduction method. However, the treatment temperatures affect the evolution of aluminothermic reaction and morphology of the materials obviously. The content, grain size and lattice parameter of TiN in materials in coke bed increased with the increase of treatment temperature. Thermodynamic calculation confirmed that metal Al reacted with O2 in coke bed while it was involved in aluminothermic reduction reaction, causing the lack of Al and surplus rutile in the products.