Titanium Alloy Matrix Composites Research Articles

Heat treatment effects on the shear performance and microstructure evolution of W-core SiC fibers

SiC fiber reinforced titanium alloy matrix composites employed in elevated temperature aeroengine components are subjected to complex loading conditions. Investigating the shear performance of SiC fibers after heat treatment can help ensure the load-carrying capability of composites at service temperatures. This study presents a novel double shear testing method for W-core SiC fibers. The shear strength and stiffness of the SiC fibers in as-received and heat-treated conditions were measured. The morphologies of SiC fibers’ shear fracture surfaces and C coatings were thoroughly analyzed. The evolution of the internal microstructure and the composition of reaction layers after heat treatments were investigated. The shear strength of W-core SiC fibers at 95% survival probability reached 588.64MPa after 200 h of heat treatment at 600°Celsius, representing a 55% improvement over both the as-received and 1100°Celsius heat-treated conditions. After heat treatment at 1100°Celsius, the reaction layer between the W core and the SiC sheath thickened exponentially due to extensive elemental diffusion, resulting in the formation of numerous Kirkendall voids. The voids facilitated crack initiation and propagation, leading to a deterioration in fiber shear performance. The insights gained in this study regarding the shear properties of SiC fibers can provide support for predicting the mechanical performance of composites under complex loading conditions.

Fabrication and Characterization of In Situ Ti-6Al-4V/TiB Composites by the Hot-Pressing Method using Recycled Metal Chips

In this study, a Ti-6Al-4V matrix composite reinforced with in situ synthesized TiB whiskers has been successfully produced from wasted chips by a cost-effective powder metallurgy route combining rapid heating and hot pressing. The effect of boron powder addition (1 vol.%, 3 vol.%, 5 vol.%, and 7 vol.%) on phase constituents, microstructures, and mechanical properties of the fabricated composites was investigated. Additionally, the effect of two different post-heat treatments on the 3 vol.% boron-containing composites was also explored. The results show that the ultimate tensile strength (UTS) and yield strength (YS) of the composite first increase when the content of boron is less than 3 vol.%, and then start to decrease with the further increase of boron content. The TiB reinforcement layers change from discontinuous to quasi-continuous and then to continuous with increasing boron content, which is attributed to a higher fraction of agglomerated TiB reinforcement phases. The composites with 1 vol.% (UTS of 1085 MPa, strain to fracture of 5.83%) and 3 vol.% (UTS of 1127 MPa, strain to fracture of 3.98%) boron powder addition show optimized tensile properties. The mechanical properties of 3 vol.% boron-containing composites are not significantly improved after heat treatment. Our experimental results demonstrate the feasibility of fabricating low-cost, high-performance titanium alloy matrix composites from Ti-6Al-4V machining chips. It can serve as a promising and cost-effective method to directly utilize Ti-6Al-4V chips to fabricate strong and ductile Ti-6Al-4V composites for niche applications.

Assessment of Nanomechanical and Tribological Performance of Refractory Nitride-Reinforced Titanium Alloy Matrix Composites Developed by Spark Plasma Sintering

Assessment of Nanomechanical and Tribological Performance of Refractory Nitride-Reinforced Titanium Alloy Matrix Composites Developed by Spark Plasma Sintering

Mechanical properties of casting titanium alloy matrix composites reinforced by WC and TiB2 ceramic particulates

Casting Titanium alloys with Wc and TiB2 additives have their mechanical characteristics examined in this work. The mechanical properties of aged titanium alloys are very impressive. UTS reach 406 MPa and YS of 253 MPa and an El of 7.4 percent. Pinned primary Wc and TiB2 phases reduced fineness by more than half, while enhancing assorted nucleation on Wc and TiB2 initial phases boosted nucleation and growth resistance. Following the heat treatment, foundational designed with the intent emerged from the substrate. There are no more stages in the shell. Those alloys containing Wc, on the other hand, have cores composed of Wc and TiB2. From 0.1 wt% to 0.2 wt% of Wc and TiB2 content, core radius rises, but shell width does not appear to change, and particle density does not appear to be altered. In time, composite particles became coarser, but their core dimensions stayed nearly same. As predicted, the exponent (n-1) is less than the expected value of 0.33, Perhaps this is because of the low temperature, which prevents a developed a semi state from emerging. The kinetics are consistent with the KV model's predictions.

Effect of reinforcement content on microstructures and mechanical properties of graphene nanoflakes-reinforced titanium alloy matrix composites

In this study, we prepared nickel and phosphorus decorated graphene nanoflakes (Ni–P@GNFs) as a reinforcement in Ti–6Al–4V (TC4) alloy matrix by an electroless plating method. It can enhance the interface bonding force between GNFs and TC4 matrix, and facilitate uniform dispersion of the GNFs in the TC4 matrix. This in turn relieve severe interface reactions between the metal and the carbon nanomaterial. The Ni–P@GNFs/TC4 composites with different GNFs content (0, 0.25, 0.5, 0.75, 1, 1.5 wt.%) were fabricated via short-term ball milling and spark plasma sintering (SPS). The effects of reinforcement content on microstructures and mechanical properties of Ni–P@GNFs/TC4 composites were studied while the sintered composites were characterized by X-Ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results indicated that the mechanical properties of Ni–P@GNFs/TC4 composites were dramatically improved due to the homogeneous dispersion of GNFs in the TC4 matrix. The compressive strength of 0.5 wt.% Ni–P@GNFs/TC4 composite reaches 1133 MPa: this was an increase of 30.6% versus TC4 (867 MPa) while maintaining 34.2% ductility. The strengthening mechanism of the mechanical properties of the composites are discussed.

Preparation and mechanical properties of titanium alloy matrix composites reinforced by Ti3AlC and TiC ceramic particulates

Ti3AlC2 MAX phase ceramic particles were used to reinforce Ti-6.5Al-2Zr-1Mo-1 V (TA15) alloy. The composites with a network architecture were prepared by low-energy ball milling (LEBM) and spark plasma sintering techniques. The effects of Ti3AlC2 content (0.5–2.0 wt%) on the microstructure, mechanical properties and wear resistance of the composites was investigated. Experimental results showed that Ti3AlC2 particles were uniformly adhered to the surface of the spherical TA15 powders after the LEBM process. The Ti3AlC2 MAX phase was reacted with the TA15 matrix and in-situ generated Ti3AlC and TiC phases after the SPS processing. The reinforcements were distributed around the interface of TA15 matrix in a 3D network architecture. The hardness, tensile strength and compressive strength of the Ti3AlC/TiC/TA15 composites were enhanced significantly without much loss of ductility. Superior mechanical properties (tensile yield strength of 958 MPa and compressive yield strength of 1271 MPa), acceptable ductility (8.56%) and Vickers microhardness (369.7 HV) were achieved in the 1.0 wt% Ti3AlC2/TA15 composites with the quasi-continues network microstructure. The wear resistance of the Ti3AlC/TiC/TA15 composites was improved due to the high hardness and high strength as well as the self-lubricating of the MAX phase.

Titanium-Alloy Metal Matrix Composites Produced by Low-Temperature Superplastic Pressure Welding

The production of strong metal matrix composites by pressure welding at low temperatures is considered. Failure of the composite is analyzed. It is found that the strength of a composite produced at 700°C may exceed that of a composite produced at 900°C.

Extremely high beta-transus temperature of graphene oxide reinforced high-temperature titanium alloy matrix composite

The beta-transus temperatures (Tβ) of graphene oxide (GO) reinforced high-temperature titanium alloy matrix composites were studied by metallography method. With the increase of GO content, Tβ increases linearly when the content of GO is 0–0.17 wt%, and then stays flat when the content is 0.17–0.23 wt%. The Tβ of the composite with only 0.17 wt% GO is up to 1132.5 ± 2.5 °C, which is 80 °C higher than the matrix alloy without GO. After heat treatment, most GO flakes were located at the interface between primary α phase and transformed β phase. The main reason for Tβ increase is that GO hindered atomic diffusion and α/β interface migration.

Fabrication and mechanical properties of network structured titanium alloy matrix composites reinforced with Ti2AlC particulates

Network structured Ti-6.5Al–2Zr–1Mo–1V (TA15) matrix composites reinforced with Ti2AlC particles were fabricated by low energy ball milling and subsequent spark plasma sintering (SPS). Microstructures, mechanical properties, and wear resistance properties of the composites were evaluated as a function of Ti2AlC weight fraction. Experimental results showed that the fine Ti2AlC powders were adhered on the surface of the spherical TA15 powders after low-energy milling process and Widmanstatten α+β microstructure with a network architecture was formed after SPS. The Ti2AlC reinforcements were reacted with Ti matrix and formed a Ti3AlC phase at the interface. The hardness, tensile, and compressive strength of the TA15/Ti3AlC composites show significant improvement with less ductility loss. The TA15/1.0 wt% Ti2AlC exhibited tensile yield strength of 929 MPa and ultimate tensile strength of 1013 MPa with ductility of 13.06%. The TA15/Ti3AlC composites had a lower friction coefficient and decreased wear rate with delamination and abrasive wear modes.

Effect of graphene nanoplatelets on tribological properties of titanium alloy matrix composites at varying sliding velocities

This paper aims to investigate the effect of graphene nanoplatelets on tribological properties of Titanium alloy (Ti-3Al-5Mo-4.5V-2Cr-1Nb-1B) (TC16) at different sliding velocities. TC16 alloy containing 1.5 wt% graphene nanoplatelets (GNPs) (TAG) had been fabricated using spark plasma sintering (SPS) technique, and the tribological tests were conducted using a ball-on-disc high-temperature tribometer. The morphologies and compositions of worn surfaces of TAG were observed at various sliding velocities using electron probe microanalysis (EPMA). Moreover, subsurface morphologies were observed using field emission electron microscope (FESEM). At a lower sliding velocity, the material transfer from the counterpart ball to the specimen was found, and tearing behavior of graphene film also occurred which lead to the severe wear and higher friction coefficient. The friction coefficient and wear rate were recorded the minimum values at higher sliding speed due to the formation of continuous graphene film, and plastic deformation was also least. Moreover, the optimum sliding speed could promote the formation of graphene lubricating film to achieve good lubricating effect. With the increase of sliding speed, the enhancement of tribological properties of graphene nanoparticles can open the door for titanium alloys to be used as cutting tools and other high speed friction applications.

Development of a Low Cost Process for Manufacturing of Ti-MMC by Roll-Diffusion-Bonding

Titanium-alloy matrix composites (TMC) are nowadays one of the material class with the highest specific resistance from room temperature up to 800° C. Centro Sviluppo Materiali SpA (CSM) efforts have been focused on the developing of an innovative solution to reduce the process costs. The new approach consists in an experimental “diffusion bonding” plant for co-rolling at high temperature sheets of titanium alloy and silicon carbide monofilaments fabrics. The result is a process cost reduction of about 40% respect to HIP process. The experimental pilot plant has been proposed for patent with n° 2006A000261 on may 2006. This paper describes the pilot plant and the process results. The metallographic examination on products shows full bonded samples (100 mm wide and 1500 mm long) obtained in a work field that is at least 100 times faster than that of HIP. High temperature tensile tests have been carried on Roll Diffusion Bonded specimens and the results are reported in comparison with those obtained by Isostatic Pressing (HIP) and Thermal- Spraying (TS) processes on the same composite.

The out-of-phase thermomechanical fatigue behavior of Ultra SCS-6/Ti–24Al–17Nb– xMo (at.%) metal matrix composites

The out-of-phase thermomechanical fatigue behavior of Ultra SCS-6/Ti–24Al–17Nb–2.3Mo (at.%), Ultra SCS-6/Ti–24Al–17Nb–1.1Mo (at.%), and Ultra SCS-6/Ti–24Al–17Nb–0.6Mo (at.%) continuously-reinforced metal matrix composites (MMCs) was investigated in order to understand the effect of Mo on the microstructure and fatigue behavior of titanium–alloy–matrix composites. From the recorded stress versus cycle behavior, two failure regimes were noted. For the highest stresses examined, fatigue-dominated failure occurred. For the lowest stresses examined, a creep-dominated failure occurred. The Ultra SCS-6/Ti–24Al–17Nb–1.1Mo MMC exhibited the shortest fatigue lives for all the applied stress levels examined. The Ultra SCS-6/Ti–24Al–17Nb–2.3Mo MMC exhibited the longest fatigue lives for the lowest applied stress levels, and the Ultra SCS-6/Ti–24Al–17Nb–0.66Mo MMC exhibited the longest fatigue lives for most of the higher applied stress levels.

Normal and Abnormal Fracture Behaviors in Low-Cycle Fatigue of a Unidirectionally Reinforced SCS-6/SP-700 Composite

Titanium alloy matrix composites (TMCs) have received considerable interest as structural materials for aeronautical applications, because of their higher specific strength and stiffness. When applying TMCs at elevated temperatures, high temperature isothermal low-cycle fatigue (LCF)failure is one of critical issues to be concerned. A unidirectionally reinforced SCS-6/ SP-700 composite is a tentative target in this work, where the matrix alloy, SP-700 is a new generation high strength Titanium alloy developed by NKK Inc., and the SCS-6 is a beta-SiC fiber developed by Textron Specially Materials, respectively. A merit to employ the SP-700 is that this alloy enables to reduce a fabrication temperature, because of its capability for superplasticity at relatively lower temperatures. The 7-plies composite specimen was produced by hot isostatic pressing (HIP) at 800°C for 0.5 hrs. in vacuum, alternating layers of thin-foils of the SP-700 and the green tapes of the SCS-6 fibers, so that the fibers were uniformly distributed as a hexagonal array in the matrix. The volume fraction of the fibers in the composite is about 28 %. In this work, the following articles in a unidirectionally reinforced SCS-6/SP-700 composite have been studied and evaluated: (i)mechanical properties of the SCS-6/SP-700 composite and the matrix alloy at temperatures ranged between room temperature and 450°C; (ii) LCF lives and the failure modes of the composite and the matrix alloy at room temperature and 450°C; (iii) fiber push-out tests at elevated temperatures ranged between room temperature and 600°C, to represent the fiber/matrix interfacial strength; and (iv) observation and the characterization of the interfacial reaction zone by means of a transmission electron microscope (TEM) and an energy dispersive X-ray spectrometer (EDS). Based on these experimental results, the effects of temperature and the loading frequency on LCF failure of the SCS-6/SP-700 composite were discussed.

超塑性加工可能なTi基複合材料の開発

In development of continuous fiber reinforced titanium alloy matrix composites (TMCs) for practical applications there are some difficulties due to the enormous production cost resulting from preliminary forming and elaborate tooling for consolidation. One of the promising approaches to reducing the production cost is to apply a superplastic forming technique in manufacturing TMC parts. In the present study, superplastic-formable TMC sheets, SiC/Ti-4.5Al-3V-2Mo-2Fe (SCS-6/SP-700) composites, were newly developed, and their consolidation conditions, deformation characteristics and cavitation behavior were investigated. The TMCs were fabricated by foil/fiber/foil lamination using SP-700 sheets 0.12 mm in thickness and 4-ply SCS-6 preforms; they were consolidated by hot isostatic pressing under an Ar-gas pressure of 150 MPa at 973 to 1073 K for 2 h. In the case of the TMCs consolidated at a temperature above 1023 K, foil/foil and foil/fiber interfaces were successfully bonded, and their tensile strength at room temperature showed better reproducibility than that in the case of the TMCs consolidated at a temperature below 998 K. In preliminary tensile tests in the direction perpendicular to the fiber orientation at 1048 K, the TMCs consolidated at 1023 K showed a maximum true strain exceeding 69%. Thus, 1023 K was selected as the consolidation temperature. Deformation properties were tested by tensile tests in the direction perpendicular to the fiber orientation under a constant strain of 5×10−5 to 1×10−3 s−1 at temperatures in the range of 1023 to 1073 K. The TMC showed superplasticity with the maximum m-value of 0.58 at 1048 K. A maximum true strain exceeding 69% was achieved under a constant strain of 5×10−5 s−1 at 1048 K. Cavitations observed in specimens after deformation were classified into three types; one of these strongly depends on the forming conditions, but the other two do not. SCS-6/SP-700 composites were successfully bent both in the longitudinal direction and in the transverse direction at 1048 K.

High temperature mechanical behaviour of titanium alloy matrix composites: J.H.Zhu et al. (Oak Ridge National Laboratory, Oak Ridge, USA.) Metall. Mater. Trans, A, vol 30A, no 6, 1999, 1569–1578

High temperature mechanical behaviour of titanium alloy matrix composites: J.H.Zhu et al. (Oak Ridge National Laboratory, Oak Ridge, USA.) Metall. Mater. Trans, A, vol 30A, no 6, 1999, 1569–1578

Ti基複合材料ブレードの開発

The high specific strength and stiffness of titanium alloy matrix composites (TMCs) with continuous fiber reinforcement are attractive for aerospace structural applications. However, the enormous production cost of TMCs is a serious impediment to their practical applications. One promising approach to reduce the production cost is the application of a superplastic forming technique to TMC parts manufacturing. A series of superplastic-formable TMC sheets, SiC/Ti-4.5Al-3V-2Mo-2Fe (SCS-6/SP-700) composites, were developed, and both their superplastic deformation and the defects generated during this deformation were investigated. The diaphragm-forming method (DFM) was adopted of a superplastic forming technique to reduce the tensile flow stress generated in the TMC sheet during deformation, and using this technique blade-shaped models were successfully fabricated without any observable defects in the fiber/matrix interface. In this study, TMC blades for an aerospace engine have been developed using DFM, and their burst strength was evaluated by a spin test. TMC sheets with 39-ply SCS-6 were formed by DFM and isothermal forging. Two SP-700 root blocks were attached to the deformed TMC by means of vacuum hot pressing. This near-net-shaped composite was machined to the final configuration. While no defects were observed by optical microscopy in the TMC blades, several un-bonded areas were found in the diffusion-bonded interfaces. The configuration of these interfaces was complex, and the plastic deformation of the matrices did not confer sufficient contact between the mating surfaces due to one-directional loading of the pressing. As the result of the spin test, the TMC blades burst at a tip speed of 782 m/s, which was 11% lower than the expected speed based on the material data. The break originated in an un-bonded area.

319 Ti基複合材料ブレードの低コスト製造プロセス開発(OS セラミックス,CMC及びMMC)

In development of continuous fiber reinforced titanium alloy matrix composites (TMCs), the enormous production cost resulting from preliminary forming and elaborate tooling for consolidation is the fatal difficulty for practical application. In order to reduce the production cost, superplastic-formable TMC sheets (SCS-6/Ti-4.5Al-3V-2Fe-2Mo) were developed, and deformation characteristics and cavitation behavior were investigated. In this study a new low-cost-manufacturing process for titanium matrix composite blade has been developed. This process consists of three steps : (i) consolidation of flat TMC panels of 20mm thickness, (ii) superplastic forming to twist the TMC panel and (iii) machining of the twisted TMC to a final blade configuration. Using this process, production cost of a TMC blade can be reduced to 1/5 of the cost for the TMC blade fabricated by the conventional manufacturing process.

Tensile properties of duplex metal-coated SiC fiber and titanium alloy matrix composites

SiC(SCS-6) fiber-reinforced titanium alloy matrix composites have a great potential for high-temperature aerospace structural applications. It is known that the interface reaction between the outermost SCS coating and Ti alloy matrix takes place during the fabrication process, and the formed reaction layer consists of a nonstoichiometric carbide (TiC{sub 1{minus}x}) and silicides (Ti{sub x}Si{sub y}). The reaction layer is brittle; however, this has only a slight effect on the quasi-static tensile strength. On the other hand, the effect of the reaction layer cracking on the fatigue damage evolution is quite severe. Such cracking under a cyclic fatigue loading condition leads to debonding of the SCS coating layer from the SiC fiber surface, which leads to a significant reduction in the fiber strength, because the debonding increases stress concentration at the SiC fiber surface, which originates from surface flaws of the fiber.

A MODEL TO PREDICT THE FATIGUE LIFE OF FIBRE‐REINFORCED TITANIUM MATRIX COMPOSITES UNDER CONSTANT AMPLITUDE LOADING

Abstract—A model based on micro‐mechanical concepts has been developed for predicting fatigue crack growth in titanium alloy matrix composites. In terms of the model, the crack system is composed of three zones: the crack, the plastic zone and the fibre. Crack tip plasticity is constrained by the fibres and remains so until certain conditions are met. The condition for crack propagation is that fibre constraint is overcome when the stress at the location of the fibre ahead of the crack tip attains a critical level required for debonding. Crack tip plasticity then increases and the crack is able to propagate round the fibre. The debonding stress is calculated using the shear lag model from values of interfacial shear strength and embedded fibre length published in the literature.If the fibres in the crack wake remain unbroken, friction stresses on the crack flanks are generated, as a result of the matrix sliding along the fibres. The friction stresses (known as the bridging effect) shield the crack tip from the remote stress, reducing the crack growth relative to that of the matrix alone. The bridging stress is calculated by adding together the friction stresses, at each fibre row bridging the crack, which are assumed to be a function of crack opening displacement and sliding distance at each row. The friction stresses at each fibre row will increase as the crack propagates further until a critical level for fibre failure is reached. Fibre failure is modelled through Weibull statistics and published experimental results. Fibre failure will reduce the bridging effect and increase the crack propagation rate.Calculated fatigue lives and crack propagation rates are compared with experimental results for three different materials (32% SCS6/Ti‐15‐3, 32% and 38% SCS6/Ti‐6‐4) subjected to mode I fatigue loading. The good agreement shown by these comparisons demonstrates the applicability of the model to predict the fatigue damage in Ti‐based MMCs.

Acoustic emission and fiber damage in creep of a unidirectional [formula omitted] metal matrix composite at 450°C

Metal matrix composites (i.e., MMCs) have potentially for high temperature applications because of light weight, high stiffness and good heat resistance. Especially titanium alloy matrix composites reinforced with continuous SiC fibers are expected to have excellent applications at high temperature, and such MMCs have been tested under tensile, compressive and cyclic loadings to evaluate high temperature strength. The present authors performed creep tests of a unidirectional SCS-6/Ti-15-3 MMC at 450 C. They found that it exhibits creep deformation and rupture in longitudinal creep at stress levels much lower than the tensile strength though the reinforcing phase, SCS-6 by Textron, does not creep at the test temperature. This experimental result can be explained as follows: At high temperature, stress in the matrix is relaxed, and accordingly stress in the fibers is increased, as was analyzed by Goto and McLean. Then, fiber breakage may occur progressively, starting from the weakest fiber, and if a certain number of fibers are thus broken, overall rupture can be induced. It is obvious that this creep rupture takes place more easily under higher applied stress, and that it is promoted if the fibers suffer from damage such as cracking in the reaction zone, degradation of themore » coating layer, and so on. Monitoring of AE (i.e., acoustic emission) can be effective in verifying the creep rupture process mentioned above. Neu and Roman monitored AE during thermomechanical fatigue tests of a unidirectional SCS-6/TIMETAL[reg sign]21S MMC, and they showed how effective this method is. In the present work, first the authors monitored AE in creep tests of a 6-ply unidirectional SCS-6/Ti-15-3 MMC at 450 C. Then, to examine the damage evaluation based on AE monitoring, the authors observed fibers exposed by etching the outer matrix layers in the crept specimens.« less