This research explored the hot deformation behavior of TiBw/(TA15-Si)composite with a network structure fabricated by hot pressing sintering.Hot compression test was conducted at 1000–1020°C under strain rate o...This research explored the hot deformation behavior of TiBw/(TA15-Si)composite with a network structure fabricated by hot pressing sintering.Hot compression test was conducted at 1000–1020°C under strain rate of 1–0.001 s^(−1).The microstructure evolution and deformation mechanisms were revealed through parent phase reconstruction.During the deformation,Dynamic Recrystallization(DRX)was preferentially developed in TiBw rich region due to the TiBw supplying dislocation pile-up and heterogeneous nucleation sites.The main DRX mechanisms included continuous and discontinuous DRX.The microstructure in TiBw lean region was closely related to strain rates,which was deformed microstructure at high strain rates but DRXed microstructure at low strain rates.The primary mechanisms of deformation were governed by dislocation motion.Besides,in TiBw rich region,Grain Boundary Sliding(GBS)coordinated the deformation due to DRX.However,GBS was hindered again at low strain rates due to the increase of DRXed grain size,contributing to a gradual rise in flow stress.展开更多
Graphene is considered promising reinforcement for improving the mechanical properties of the titanium alloys.However,overcoming the strength-ductility trade-off in graphene-reinforced titanium composites remains a ch...Graphene is considered promising reinforcement for improving the mechanical properties of the titanium alloys.However,overcoming the strength-ductility trade-off in graphene-reinforced titanium composites remains a challenge.In this study,the high-performance graphene nanoplatelets(GNPs)reinforced Ti-6Al-4V(TC4)matrix composites were successfully synthesized by combining the hot-pressing sintering and hot-rolling methods.Studies on the effect of GNPs on microstructures and properties of the as-sintered and as-rolled TC4 composites were systematically conducted.It indicates that the strength of the composites can be substantially enhanced by the addition of GNPs,primarily attributable to grain refinement and the pinning effect induced by in situ formed TiC particles.Moreover,the increase in the GNPs content results in a decrease in the plasticity of the as-sintered composites due to the aggregation of TiC.Additionally,hot rolling synchronously enhances the strength and plasticity of the composites by facilitating the homogeneous dispersion of TiC within the TC4 matrix.This work provided a potential strategy in designing the graphene-reinforced TC4 matrix composites with superior strength-ductility synergy.展开更多
In this study,AZ91D(Mg-9Al-Zn)alloys reinforced with 2 vol%TC4(Ti-6Al-4V)particles fabricated by semi-solid stir casting were extruded at different ratios,resulting in observed grain refinement effects.The research fi...In this study,AZ91D(Mg-9Al-Zn)alloys reinforced with 2 vol%TC4(Ti-6Al-4V)particles fabricated by semi-solid stir casting were extruded at different ratios,resulting in observed grain refinement effects.The research findings demonstrate that both TC4 andβ-Mg_(17)Al_(12) phases contribute to promoting dynamic recrystallization(DRX)nucleation.With increasing extrusion ratio,theβ-phase(Mg_(17)Al_(12))gradually fractures into smaller particles,leading to progressive grain refinement.Furthermore,the transition from〈01-10〉fiber texture to non-basal texture in theα-Mg matrix after hot extrusion is attributed to improved DRX behavior and activation of non-basal slip.As the extrusion ratio increases,the tensile strength and elongation(EL)of TC4_(p)/AZ91D composite improve significantly,reaching optimum comprehensive mechanical properties at an extrusion of 40:1 with a yield strength(YS)of 257 MPa,an ultimate tensile strength(UTS)of 357 MPa,and an EL of 9.7%.This remarkable strengthening effect is primarily attributed toβ-phase reinforcement,grain refinement strengthening,and strain hardening.展开更多
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 h...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.展开更多
The effects of current pulsing on the microstructure, hardness and tensile properties at different temperatures of gas tungsten arc （GTA） weldments of titanium matrix composites were studied. Full-penetration butt j...The effects of current pulsing on the microstructure, hardness and tensile properties at different temperatures of gas tungsten arc （GTA） weldments of titanium matrix composites were studied. Full-penetration butt joints were made with or without current pulsing. Optical microscopy, hardness test and scanning electron microscopy were employed to evaluate the metallurgical characteristics of welded joints. Tensile properties of weldments at different temperatures were studied and correlated with the microstructure. The results exhibit that current pulsing leads to the refinement of the weld microstrucmre and TiB whisker and the redistribution of reinforcements resulting in higher hardness, tensile strength and ductility of weldments in the as-welded condition.展开更多
The oxidation behavior of Ti55 alloy and TiBw/Ti55 composites at temperatures ranging from 960 to 1000℃ was investigated by characterizing the surface and cross-section microstructure of specimens.Results showed that...The oxidation behavior of Ti55 alloy and TiBw/Ti55 composites at temperatures ranging from 960 to 1000℃ was investigated by characterizing the surface and cross-section microstructure of specimens.Results showed that TiBw reinforcement accelerated the occurrence of Ti_(6O)/Ti_(3O) by dissolving oxygen in titanium in the starting oxidation stage,and the Ti_(6O)/Ti_(3O) transformed into TiO_(2) with the progression of oxidation.Meanwhile,TiBw reinforcement promoted the formation of(101)crystal planes to be beneficial to the growth of TiO_(2) twins.The cross-sectional characterization showed that the oxide layer of Ti55 alloy and TiBw/Ti55 composites from outside to inside was TiO_(2)+Al_(2)O_(3),TiO_(2),Ti-Sn compounds,Ti_(6O)/Ti_(3O) in sequence,which was confirmed by calculating the standard Gibbs free energy of the oxide nucleation.The TiBw reinforcement accelerated the occurrence of suboxides Ti_(6O)/Ti_(3O) by dissolving oxygen in titanium,and promoted the formation of(101)crystal planes which were beneficial to the growth of TiO_(2) twins.The optimal addition of TiBw induced the TiO_(2) twins,promoted the random orientation of oxides and refined the oxide size of the TiBw/Ti55 composites with 3.5%volume fractions of TiBw,resulting in the best resistance against oxidation.展开更多
To assess the high-temperature creep properties of titanium matrix composites for aircraft skin,the TA15 alloy,TiB/TA15 and TiB/(TA15−Si)composites with network structure were fabricated using low-energy milling and v...To assess the high-temperature creep properties of titanium matrix composites for aircraft skin,the TA15 alloy,TiB/TA15 and TiB/(TA15−Si)composites with network structure were fabricated using low-energy milling and vacuum hot pressing sintering techniques.The results show that introducing TiB and Si can reduce the steady-state creep rate by an order of magnitude at 600℃ compared to the alloy.However,the beneficial effect of Si can be maintained at 700℃ while the positive effect of TiB gradually diminishes due to the pores near TiB and interface debonding.The creep deformation mechanism of the as-sintered TiB/(TA15−Si)composite is primarily governed by dislocation climbing.The high creep resistance at 600℃ can be mainly attributed to the absence of grain boundaryαphases,load transfer by TiB whisker,and the hindrance of dislocation movement by silicides.The low steady-state creep rate at 700℃ is mainly resulted from the elimination of grain boundaryαphases as well as increased dynamic precipitation of silicides andα_(2).展开更多
Metal matrix composites tiles based on Ti-6Al-4V(Ti64)alloy,reinforced with 10,20,and 40(vol%)of either TiC or TiB particles were made using press-and-sinter blended elemental powder metallurgy(BEPM)and then bonded to...Metal matrix composites tiles based on Ti-6Al-4V(Ti64)alloy,reinforced with 10,20,and 40(vol%)of either TiC or TiB particles were made using press-and-sinter blended elemental powder metallurgy(BEPM)and then bonded together into 3-layer laminated plates using hot isostatic pressing(HIP).The laminates were ballistically tested and demonstrated superior performance.The microstructure and properties of the laminates were analyzed to determine the effect of the BEPM and HIP processing on the ballistic properties of the layered plates.The effect of porosity in sintered composites on further diffusion bonding of the plates during HIP is analyzed to understand the bonding features at the interfaces between different adjacent layers in the laminate.Exceptional ballistic performance of fabricated structures was explained by a significant reduction in the residual porosity of the BEPM products by their additional processing using HIP,which provides an unprecedented increase in the hardness of the layered composites.It is argued that the combination of the used two technologies,BEPM and HIP is principally complimentary for the materials in question with the abilities to solve the essential problems of each used individually.展开更多
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 t...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.展开更多
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. Th...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.展开更多
In-situ TiC and remained multi-walled carbon nanotubes（MWCNTs） reinforced Ti composites were synthesized using vacuum hot-press sintering and hot rolling. The effect of weight fraction of MWCNTs on microstructural e...In-situ TiC and remained multi-walled carbon nanotubes（MWCNTs） reinforced Ti composites were synthesized using vacuum hot-press sintering and hot rolling. The effect of weight fraction of MWCNTs on microstructural evolution and mechanical properties of the Ti composites was investigated. The results indicated that both proportion and particle size of TiC increased in proportion to MWCNTs content, which resulted in different matrix microstructure, and the grains were obviously refined after rolling deformation. The hardness tests indicated that MWCNTs addition could make the composites harden, and 18.4%improvement in hardness was obtained after hot rolling. The significant improvement in both strength and hardness could be attributed to grain refinement, solid solution strengthening of carbon and dispersion strengthening of TiC particles and remained MWCNTs. A good combination of strength and ductility were achieved in Ti–1 wt% MWCNTs composites, which were in accordance with the uniform distribution of smaller-sized TiC particles in Ti matrix.展开更多
Further improvement on high temperature durability is one of the most important aims except for high specific strength, high specific stiffness, and excellent wear resistance, to design and fabricate discontinuously r...Further improvement on high temperature durability is one of the most important aims except for high specific strength, high specific stiffness, and excellent wear resistance, to design and fabricate discontinuously reinforced titanium matrix composites （DRTMCs）. Their superior properties render them extensive application potential in aerospace and military industries due to the urgent demand for the materials with characteristics of lightweight, high strength, high stiffness and high temperature durability. With development on fabrication methods and room temperature properties, testing, characterizing, evaluating and further increasing high temperature properties of DRTMCs are becoming more and more important to promote their applications. This review provides insights and comprehensions on the high temperature tensile properties, superplastic tensile properties, creep behaviors, and high temperature oxidation behaviors of DRTMCs,展开更多
This work focused on the influence of TiC reinforcing particles on the tribological properties of titanium matrix composites(TMCs)with open porosity,processed by spark plasma sintering(SPS).Materials composed of an eq...This work focused on the influence of TiC reinforcing particles on the tribological properties of titanium matrix composites(TMCs)with open porosity,processed by spark plasma sintering(SPS).Materials composed of an equimolar mixture of Ti and TiH2 with 0,3,10 and 30 vol.% of TiC were sintered at 850 ℃.Nanoindentation and wear tests were carried out to assess the nanohardness and the wear resistance in a tribometer with a reciprocating sliding ball-on-flat configuration.Results showed a nanohardness increment from 5 to 14 GPa with increasing TiC content.The coefficient of friction(CoF)showed a minimum of 0.2 for 10% TiC grade,which also showed the lowest wear rate.For the low TiC content sample,adhesive wear with severe plastic deformation was identified.Meanwhile,medium content TiC sample showed a mechanical mixed layer(MML),whereas high TiC content composite showed abrasive as the main wear mechanism.In conclusion,the wear mechanisms,CoFs and wear volume changed with TiC content.展开更多
In order to elucidate the microstructure evolution and silicide precipitation behavior during high-temperature deformation,TiB reinforced titanium matrix composites were subjected to isothermal hot compression at 950...In order to elucidate the microstructure evolution and silicide precipitation behavior during high-temperature deformation,TiB reinforced titanium matrix composites were subjected to isothermal hot compression at 950℃,strain rate of 0.05 s^(−1) and employing different strains of 0.04,0.40,0.70 and 1.00.The results show that with the increase of strain,a decrease in the content,dynamic recrystallization of theαphase and the vertical distribution of TiB along the compression axis lead to stress stability.Meantime,continuous dynamic recrystallization reduces the orientation difference of the primaryαphase,which weakens the texture strength of the matrix.The recrystallization mechanisms are strain-induced grain boundary migration and particle stimulated nucleation by TiB.The silicide of Ti_(6)Si_(3) is mainly distributed at the interface of TiB andαphase.The precipitation of silicide is affected by element diffusion,and TiB whisker accelerates the precipitation behavior of silicide by hindering the movement of dislocations and providing nucleation particles.展开更多
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） metho...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.展开更多
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 re...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.展开更多
The consolidation process of SiC<sub>f</sub>/Ti-6Al-4V composites by matrix-coated fiber (MCF) method via hot pressing was investigated using finite element modeling (FEM). By analyzing the elastic–plasti...The consolidation process of SiC<sub>f</sub>/Ti-6Al-4V composites by matrix-coated fiber (MCF) method via hot pressing was investigated using finite element modeling (FEM). By analyzing the elastic–plastic contact deformation of the representative aligned coated fibers, the consolidation maps delineating the time–temperature–pressure relationship for full densification were constructed. Both the flow coefficient and the contact area coefficient used to describe the contact deformation were calculated according to the model. In addition, the effect of fiber content on matrix stress distribution was analyzed. The results show that fiber content is a significant factor that influences the densification process. Higher fiber content will lower the consolidation rate.展开更多
Considerable studies on processed pure titanium and titanium alloys have proved the possibility of prop-erty anisotropy induced by crystallographic textures,but limited information is available for the intrinsic coupl...Considerable studies on processed pure titanium and titanium alloys have proved the possibility of prop-erty anisotropy induced by crystallographic textures,but limited information is available for the intrinsic coupling of matrix and reinforcement textures and their synergistic effect on property anisotropy in tita-nium matrix composite(TMCs).In the present work,an advanced EBSD/EDS coupling method was used to investigate the formation mechanism of primaryαand secondaryαtextures in the matrix alloy.It is revealed for the first time that the reinforcement TiB_(w)displays a{100}<010>texture after hot rolling and has little effect on the matrix texture component but weakens texture intensity.Significant anisotropies in the tensile strength and ductility can be all noted at room and high-temperatures,which is the syn-ergistic effect of the matrix texture and the aligned TiB_(w).The mean Schmid factor of each slip system was calculated to evaluate the influence of matrix texture on the minimum active stress of slip deforma-tion in the different tensile directions.The analysis shows that the strong T-type matrix texture results in higher strength but lower ductility when loaded in the transverse direction.Moreover,a generalized shear-lag model was modified to quantitatively evaluate the strengthening contribution of aligned TiB_(w),which decreases with increasing off-axis angle and test temperature.A new parameter,defined as the critical aspect ratio of the off-axis whisker,was proposed to rationalize why the TiB_(w) failure mechanism converts from TiB_(w) fracture to TiB_(w)/matrix interfacial debonding with increasing off-axis angle and test temperature.展开更多
The wear tests of titanium matrix composites(TMCs)at the loads of 50,100,120,and 150 N were carried out with an MMW-1 vertical universal friction and wear tester to study the addition of multilayer graphene(MLG)/nano-...The wear tests of titanium matrix composites(TMCs)at the loads of 50,100,120,and 150 N were carried out with an MMW-1 vertical universal friction and wear tester to study the addition of multilayer graphene(MLG)/nano-Fe2O3 composites(0,0.1,0.2,0.3,0.4,and 0.5 g)on the dry sliding wear behavior of TMCs.TMCs presented a marked variation in wear loss as a function of the amount of MLG/Fe2O3 addition,and a significant decrease in the friction coefficient was obtained,reducing this parameter up to 50%.With the rise and fall of wear loss,TMCs underwent a transition from severe wear to mild wear.These phenomena were attributed to the existence of a protective lubricating film,which prevented the surface from coming in direct contact,and the lubricating film was 15-20μm thick and made up of MLG/Fe2O3(1:2)nanocomposites.Its structure was speculated to be similar to a rolling wood.展开更多
（TiCp＋ TiBw）/Ti-6Al-4V titanium matrix composites（PTMCs） have broad application prospects in the aviation and nuclear field. However, it is a typical difficult-to-cut material due to high hardness of the reinforc...（TiCp＋ TiBw）/Ti-6Al-4V titanium matrix composites（PTMCs） have broad application prospects in the aviation and nuclear field. However, it is a typical difficult-to-cut material due to high hardness of the reinforcements, high strength and low thermal conductivity of Ti-6Al-4V alloy matrix. Grinding experiments with vitrified CBN wheels were conducted to analyze comparatively the grinding performance of PTMCs and Ti-6Al-4V alloy. Grinding force and force ratios, specific grinding energy, grinding temperature, surface roughness, ground surface appearance were discussed. The results show that the normal grinding force and the force ratios of PTMCs are much larger than that of Ti-6Al-4V alloy. Low depth of cut and high workpiece speed are generally beneficial to achieve the precision ground surface for PTMCs. The hard reinforcements of PTMCs are mainly removed in the ductile mode during grinding. However, the removal phenomenon of the reinforcements due to brittle fracture still exists, which contributes to the lower specific grinding energy and grinding temperature of PTMCs than Ti-6Al-4V alloy.展开更多
基金financially supported by the National Natural Science Foundation of China(No.52375324).
文摘This research explored the hot deformation behavior of TiBw/(TA15-Si)composite with a network structure fabricated by hot pressing sintering.Hot compression test was conducted at 1000–1020°C under strain rate of 1–0.001 s^(−1).The microstructure evolution and deformation mechanisms were revealed through parent phase reconstruction.During the deformation,Dynamic Recrystallization(DRX)was preferentially developed in TiBw rich region due to the TiBw supplying dislocation pile-up and heterogeneous nucleation sites.The main DRX mechanisms included continuous and discontinuous DRX.The microstructure in TiBw lean region was closely related to strain rates,which was deformed microstructure at high strain rates but DRXed microstructure at low strain rates.The primary mechanisms of deformation were governed by dislocation motion.Besides,in TiBw rich region,Grain Boundary Sliding(GBS)coordinated the deformation due to DRX.However,GBS was hindered again at low strain rates due to the increase of DRXed grain size,contributing to a gradual rise in flow stress.
基金supported by the National Key Research and Development Program of China(No.2023YFB3711000)the National Natural Science Foundation of China(Nos.52403364,52404369,W2411048 and 52171164)+3 种基金the Youth Innovation Promotion Association CAS(No.2021188)the Excellent Youth Fund of Liaoning Province(No.2024JH3/10200022)the China Postdoctoral Science Foundation(No.2024M753302)the IMR Innovation Fund(No.2024-PY18).
文摘Graphene is considered promising reinforcement for improving the mechanical properties of the titanium alloys.However,overcoming the strength-ductility trade-off in graphene-reinforced titanium composites remains a challenge.In this study,the high-performance graphene nanoplatelets(GNPs)reinforced Ti-6Al-4V(TC4)matrix composites were successfully synthesized by combining the hot-pressing sintering and hot-rolling methods.Studies on the effect of GNPs on microstructures and properties of the as-sintered and as-rolled TC4 composites were systematically conducted.It indicates that the strength of the composites can be substantially enhanced by the addition of GNPs,primarily attributable to grain refinement and the pinning effect induced by in situ formed TiC particles.Moreover,the increase in the GNPs content results in a decrease in the plasticity of the as-sintered composites due to the aggregation of TiC.Additionally,hot rolling synchronously enhances the strength and plasticity of the composites by facilitating the homogeneous dispersion of TiC within the TC4 matrix.This work provided a potential strategy in designing the graphene-reinforced TC4 matrix composites with superior strength-ductility synergy.
基金the Guangdong Major Project of Basic and Applied Basic Research(2020B0301030006)the Guangdong Provincial Academy of Sciences Fund(2020GDASYL-20200101001)the Natural Science Foundation of Hubei Province,China(2023AFB1033).
文摘In this study,AZ91D(Mg-9Al-Zn)alloys reinforced with 2 vol%TC4(Ti-6Al-4V)particles fabricated by semi-solid stir casting were extruded at different ratios,resulting in observed grain refinement effects.The research findings demonstrate that both TC4 andβ-Mg_(17)Al_(12) phases contribute to promoting dynamic recrystallization(DRX)nucleation.With increasing extrusion ratio,theβ-phase(Mg_(17)Al_(12))gradually fractures into smaller particles,leading to progressive grain refinement.Furthermore,the transition from〈01-10〉fiber texture to non-basal texture in theα-Mg matrix after hot extrusion is attributed to improved DRX behavior and activation of non-basal slip.As the extrusion ratio increases,the tensile strength and elongation(EL)of TC4_(p)/AZ91D composite improve significantly,reaching optimum comprehensive mechanical properties at an extrusion of 40:1 with a yield strength(YS)of 257 MPa,an ultimate tensile strength(UTS)of 357 MPa,and an EL of 9.7%.This remarkable strengthening effect is primarily attributed toβ-phase reinforcement,grain refinement strengthening,and strain hardening.
基金supported by the National Natural Science Foundation of China(52071065)the Fundamental Research Funds for the Central Universities(N2007007)+1 种基金the National Key R&D Program of China(2016YFB-0301201)the Ten Technology Research Projects of Hunan Province(No.2022GK1050).
文摘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.
基金Project(51371114)supported by the National Natural Science Foundation of ChinaProject(2012CB619600)supported by the National Basic Research Program of China+1 种基金Project(10SG15)supported by the Dawn Program of Shanghai Education Commission,ChinaProject(12XD1402800)supported by Shanghai Science and Technology Committee,China
文摘The effects of current pulsing on the microstructure, hardness and tensile properties at different temperatures of gas tungsten arc （GTA） weldments of titanium matrix composites were studied. Full-penetration butt joints were made with or without current pulsing. Optical microscopy, hardness test and scanning electron microscopy were employed to evaluate the metallurgical characteristics of welded joints. Tensile properties of weldments at different temperatures were studied and correlated with the microstructure. The results exhibit that current pulsing leads to the refinement of the weld microstrucmre and TiB whisker and the redistribution of reinforcements resulting in higher hardness, tensile strength and ductility of weldments in the as-welded condition.
基金supported by the Special Project of the Central-Guided Local Science and Technology Development(Grant No.2022ZY2-JCYJ-01-06)the Key Research and Development Program(Grant No.2020-xxx-ZD-179-00-05)Prof.Lujun Huang Group at Harbin Institute of Technology for providing the TiBw/Ti55 composites.
文摘The oxidation behavior of Ti55 alloy and TiBw/Ti55 composites at temperatures ranging from 960 to 1000℃ was investigated by characterizing the surface and cross-section microstructure of specimens.Results showed that TiBw reinforcement accelerated the occurrence of Ti_(6O)/Ti_(3O) by dissolving oxygen in titanium in the starting oxidation stage,and the Ti_(6O)/Ti_(3O) transformed into TiO_(2) with the progression of oxidation.Meanwhile,TiBw reinforcement promoted the formation of(101)crystal planes to be beneficial to the growth of TiO_(2) twins.The cross-sectional characterization showed that the oxide layer of Ti55 alloy and TiBw/Ti55 composites from outside to inside was TiO_(2)+Al_(2)O_(3),TiO_(2),Ti-Sn compounds,Ti_(6O)/Ti_(3O) in sequence,which was confirmed by calculating the standard Gibbs free energy of the oxide nucleation.The TiBw reinforcement accelerated the occurrence of suboxides Ti_(6O)/Ti_(3O) by dissolving oxygen in titanium,and promoted the formation of(101)crystal planes which were beneficial to the growth of TiO_(2) twins.The optimal addition of TiBw induced the TiO_(2) twins,promoted the random orientation of oxides and refined the oxide size of the TiBw/Ti55 composites with 3.5%volume fractions of TiBw,resulting in the best resistance against oxidation.
基金financially supported by the National Key R&D Program of China(No.2022YFB3707405)the National Natural Science Foundation of China(Nos.U22A20113,52171137,52071116)+1 种基金Heilongjiang Provincial Natural Science Foundation,China(No.TD2020E001)Heilongjiang Touyan Team Program,China.
文摘To assess the high-temperature creep properties of titanium matrix composites for aircraft skin,the TA15 alloy,TiB/TA15 and TiB/(TA15−Si)composites with network structure were fabricated using low-energy milling and vacuum hot pressing sintering techniques.The results show that introducing TiB and Si can reduce the steady-state creep rate by an order of magnitude at 600℃ compared to the alloy.However,the beneficial effect of Si can be maintained at 700℃ while the positive effect of TiB gradually diminishes due to the pores near TiB and interface debonding.The creep deformation mechanism of the as-sintered TiB/(TA15−Si)composite is primarily governed by dislocation climbing.The high creep resistance at 600℃ can be mainly attributed to the absence of grain boundaryαphases,load transfer by TiB whisker,and the hindrance of dislocation movement by silicides.The low steady-state creep rate at 700℃ is mainly resulted from the elimination of grain boundaryαphases as well as increased dynamic precipitation of silicides andα_(2).
基金funding from the NATO Agency Science for Peace and Security (#G5787)Ballistic investigations were co-financed by Military University of Technology in Warsaw under research project UGB 829/2023/WATSeparate works made in G.V.Kurdyumov Institute for Metal Physics of N.A.S.of Ukraine were partially financially supported by N.A.S.of Ukraine within the frames of project#III09-18。
文摘Metal matrix composites tiles based on Ti-6Al-4V(Ti64)alloy,reinforced with 10,20,and 40(vol%)of either TiC or TiB particles were made using press-and-sinter blended elemental powder metallurgy(BEPM)and then bonded together into 3-layer laminated plates using hot isostatic pressing(HIP).The laminates were ballistically tested and demonstrated superior performance.The microstructure and properties of the laminates were analyzed to determine the effect of the BEPM and HIP processing on the ballistic properties of the layered plates.The effect of porosity in sintered composites on further diffusion bonding of the plates during HIP is analyzed to understand the bonding features at the interfaces between different adjacent layers in the laminate.Exceptional ballistic performance of fabricated structures was explained by a significant reduction in the residual porosity of the BEPM products by their additional processing using HIP,which provides an unprecedented increase in the hardness of the layered composites.It is argued that the combination of the used two technologies,BEPM and HIP is principally complimentary for the materials in question with the abilities to solve the essential problems of each used individually.
基金financially supported by the National "973" Research Project (No. 2006CB605206-1)
文摘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.
基金financially supported by the National Natural Science Foundation of China(No.51274040)the Fundamental Research Funds for the Central Universities(FRF-TP-10-003B)
文摘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.
基金supported financially by the National Natural Science Foundation of China (Nos. 51371114, 51501112 and U1602274)the Fund of the State Key Laboratory of Solidification Processing in NWPU (No. SKLSP201620)+2 种基金the Shanghai Academy of Spaceflight-Joint Research Centre of Shanghai Jiao Tong University advanced aerospace technology (No. US-CAST2012-14)the National Engineering and Research Center for Commercial Aircraft Manufacturing (No. SAMC14-JS-15-047)the 111 Project (No. B16032)
文摘In-situ TiC and remained multi-walled carbon nanotubes（MWCNTs） reinforced Ti composites were synthesized using vacuum hot-press sintering and hot rolling. The effect of weight fraction of MWCNTs on microstructural evolution and mechanical properties of the Ti composites was investigated. The results indicated that both proportion and particle size of TiC increased in proportion to MWCNTs content, which resulted in different matrix microstructure, and the grains were obviously refined after rolling deformation. The hardness tests indicated that MWCNTs addition could make the composites harden, and 18.4%improvement in hardness was obtained after hot rolling. The significant improvement in both strength and hardness could be attributed to grain refinement, solid solution strengthening of carbon and dispersion strengthening of TiC particles and remained MWCNTs. A good combination of strength and ductility were achieved in Ti–1 wt% MWCNTs composites, which were in accordance with the uniform distribution of smaller-sized TiC particles in Ti matrix.
基金financially supported by the National Natural Science Foundation of China (Nos.51101042,51271064 and 51471063)the High Technology Research and Development Program of China (No.2013AA031202)the Fundamental Research Funds for the Central Universities (No.HIT.BRETIII.201401)
文摘Further improvement on high temperature durability is one of the most important aims except for high specific strength, high specific stiffness, and excellent wear resistance, to design and fabricate discontinuously reinforced titanium matrix composites （DRTMCs）. Their superior properties render them extensive application potential in aerospace and military industries due to the urgent demand for the materials with characteristics of lightweight, high strength, high stiffness and high temperature durability. With development on fabrication methods and room temperature properties, testing, characterizing, evaluating and further increasing high temperature properties of DRTMCs are becoming more and more important to promote their applications. This review provides insights and comprehensions on the high temperature tensile properties, superplastic tensile properties, creep behaviors, and high temperature oxidation behaviors of DRTMCs,
基金The Mexican Council of Science and Technology (CONACYT) for the support received under the scholarship (449474)
文摘This work focused on the influence of TiC reinforcing particles on the tribological properties of titanium matrix composites(TMCs)with open porosity,processed by spark plasma sintering(SPS).Materials composed of an equimolar mixture of Ti and TiH2 with 0,3,10 and 30 vol.% of TiC were sintered at 850 ℃.Nanoindentation and wear tests were carried out to assess the nanohardness and the wear resistance in a tribometer with a reciprocating sliding ball-on-flat configuration.Results showed a nanohardness increment from 5 to 14 GPa with increasing TiC content.The coefficient of friction(CoF)showed a minimum of 0.2 for 10% TiC grade,which also showed the lowest wear rate.For the low TiC content sample,adhesive wear with severe plastic deformation was identified.Meanwhile,medium content TiC sample showed a mechanical mixed layer(MML),whereas high TiC content composite showed abrasive as the main wear mechanism.In conclusion,the wear mechanisms,CoFs and wear volume changed with TiC content.
基金financial supports from the National Natural Science Foundation of China (No. 51871184)the Natural Science Foundation of Shandong Province, China (No. ZR2019MEM037)+1 种基金the Zhoucun School-City Integration Development Plan, China (No. 2020ZCXCZH03)the School-city Integration Development Project of Zibo, China (No. 2019ZBXC022)。
文摘In order to elucidate the microstructure evolution and silicide precipitation behavior during high-temperature deformation,TiB reinforced titanium matrix composites were subjected to isothermal hot compression at 950℃,strain rate of 0.05 s^(−1) and employing different strains of 0.04,0.40,0.70 and 1.00.The results show that with the increase of strain,a decrease in the content,dynamic recrystallization of theαphase and the vertical distribution of TiB along the compression axis lead to stress stability.Meantime,continuous dynamic recrystallization reduces the orientation difference of the primaryαphase,which weakens the texture strength of the matrix.The recrystallization mechanisms are strain-induced grain boundary migration and particle stimulated nucleation by TiB.The silicide of Ti_(6)Si_(3) is mainly distributed at the interface of TiB andαphase.The precipitation of silicide is affected by element diffusion,and TiB whisker accelerates the precipitation behavior of silicide by hindering the movement of dislocations and providing nucleation particles.
文摘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.
基金This work was financially supported by the National Natural Science Foundation of China (No. 50205005)
文摘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.
基金financially supported by the National Natural Science Foundation of China(Nos.51071122 and51271147)
文摘The consolidation process of SiC<sub>f</sub>/Ti-6Al-4V composites by matrix-coated fiber (MCF) method via hot pressing was investigated using finite element modeling (FEM). By analyzing the elastic–plastic contact deformation of the representative aligned coated fibers, the consolidation maps delineating the time–temperature–pressure relationship for full densification were constructed. Both the flow coefficient and the contact area coefficient used to describe the contact deformation were calculated according to the model. In addition, the effect of fiber content on matrix stress distribution was analyzed. The results show that fiber content is a significant factor that influences the densification process. Higher fiber content will lower the consolidation rate.
基金financially supported by the National Natural Scienc e Foundation of China(Nos.U1602274,51875349,51871150 and 51821001)the National Key R&D Program of China(No.2018YFB1106403)+2 种基金the Medical Intersection Project of Shanghai Jiao Tong University(Nos.ZH2018QNA22 and YG2017QN28)the 111 Project(No.B16032)the Laboratory Innovative Research Pro-gram of Shanghai Jiao Tong University(No.17SJ-14).
文摘Considerable studies on processed pure titanium and titanium alloys have proved the possibility of prop-erty anisotropy induced by crystallographic textures,but limited information is available for the intrinsic coupling of matrix and reinforcement textures and their synergistic effect on property anisotropy in tita-nium matrix composite(TMCs).In the present work,an advanced EBSD/EDS coupling method was used to investigate the formation mechanism of primaryαand secondaryαtextures in the matrix alloy.It is revealed for the first time that the reinforcement TiB_(w)displays a{100}<010>texture after hot rolling and has little effect on the matrix texture component but weakens texture intensity.Significant anisotropies in the tensile strength and ductility can be all noted at room and high-temperatures,which is the syn-ergistic effect of the matrix texture and the aligned TiB_(w).The mean Schmid factor of each slip system was calculated to evaluate the influence of matrix texture on the minimum active stress of slip deforma-tion in the different tensile directions.The analysis shows that the strong T-type matrix texture results in higher strength but lower ductility when loaded in the transverse direction.Moreover,a generalized shear-lag model was modified to quantitatively evaluate the strengthening contribution of aligned TiB_(w),which decreases with increasing off-axis angle and test temperature.A new parameter,defined as the critical aspect ratio of the off-axis whisker,was proposed to rationalize why the TiB_(w) failure mechanism converts from TiB_(w) fracture to TiB_(w)/matrix interfacial debonding with increasing off-axis angle and test temperature.
基金The authors would like to acknowledge the financial support of this work by National Natural Science Foundation of China(No.51505199)Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX19_1670).
文摘The wear tests of titanium matrix composites(TMCs)at the loads of 50,100,120,and 150 N were carried out with an MMW-1 vertical universal friction and wear tester to study the addition of multilayer graphene(MLG)/nano-Fe2O3 composites(0,0.1,0.2,0.3,0.4,and 0.5 g)on the dry sliding wear behavior of TMCs.TMCs presented a marked variation in wear loss as a function of the amount of MLG/Fe2O3 addition,and a significant decrease in the friction coefficient was obtained,reducing this parameter up to 50%.With the rise and fall of wear loss,TMCs underwent a transition from severe wear to mild wear.These phenomena were attributed to the existence of a protective lubricating film,which prevented the surface from coming in direct contact,and the lubricating film was 15-20μm thick and made up of MLG/Fe2O3(1:2)nanocomposites.Its structure was speculated to be similar to a rolling wood.
基金co-supported by the National Natural Science Foundation of China (Nos. 51235004, 51375235)the Fundamental Research Funds for the Central Universities (No. NE2014103) of ChinaPriority Academic Program Development of Jiangsu Higher Education Institutions (PAPD) of China
文摘（TiCp＋ TiBw）/Ti-6Al-4V titanium matrix composites（PTMCs） have broad application prospects in the aviation and nuclear field. However, it is a typical difficult-to-cut material due to high hardness of the reinforcements, high strength and low thermal conductivity of Ti-6Al-4V alloy matrix. Grinding experiments with vitrified CBN wheels were conducted to analyze comparatively the grinding performance of PTMCs and Ti-6Al-4V alloy. Grinding force and force ratios, specific grinding energy, grinding temperature, surface roughness, ground surface appearance were discussed. The results show that the normal grinding force and the force ratios of PTMCs are much larger than that of Ti-6Al-4V alloy. Low depth of cut and high workpiece speed are generally beneficial to achieve the precision ground surface for PTMCs. The hard reinforcements of PTMCs are mainly removed in the ductile mode during grinding. However, the removal phenomenon of the reinforcements due to brittle fracture still exists, which contributes to the lower specific grinding energy and grinding temperature of PTMCs than Ti-6Al-4V alloy.
