Continuous fibre reinforced titanium and aluminium composites: a comparison

Materials Science and Engineering A263 (1999) 305 – 313

Continuous fibre reinforced titanium and aluminium composites: a comparison A. Vassel ONERA, Materials Systems and Composites Department, BP 72, 92322 Chaˆtillon Cedex, France

Abstract Continuous fibre reinforced metal matrix composites are potential candidates for advanced aerospace systems due to the ever-increasing performance requirements. This paper surveys the processing routes and mechanical properties of unidirectionally reinforced titanium-based (Ti–MMCs) and aluminium-based (Al – MMCs) composites. Due to the high melting point of titanium and its strong chemical reactivity, Ti–MMCs are processed via solid state routes and large diameter fibres are employed. Unlike Ti–MMCs, the low melting point of aluminium enables the fabrication of Al – MMCs via liquid routes and small diameter fibres can be used. The mechanical properties of recently developed Ti – MMCs and Al – MMCs are compared; the influence of the temperature and the loading direction are highlighted. © 1999 Elsevier Science S.A. All rights reserved. Keywords: Fibre reinforced metal matrix composites; Titanium; Aluminium

1. Introduction Metal matrix composites are one of several classes of advanced materials which are expected to play a significant role in the development of future aerospace applications. Due to the availability of high performance continuous fibres, these composites exhibit much improved properties, in terms of specific strengths and stiffness at room and elevated temperatures, compared to unreinforced structural materials. Among metal matrix composites, continuous fibre reinforced titaniumbased (Ti–MMCs) and aluminium-based composites (Al–MMCs) are of particular interest. Potential applications of Ti – MMCs are future aeroengines where their high temperature properties are attractive for compressor discs, blades, shafts and casings. The compressor bling (bladed ring) is the application which is seen to yield the greatest benefit from the use of Ti–MMCs. Weight savings of up to 40% have been predicted for a Ti – MMC compressor bling when compared with conventional titanium alloy blisk (bladed disc) designs [1]. Continuous fibre reinforced Al–MMCs are being developed for two main product classes: net-shape casting of reinforced components and continuously produced reinforced structural shapes such as wires, rods, I-beams or T-sections. Using Al– MMCs as a local reinforcement, the performance of the

low-cost aluminium casting may be dramatically improved [2]. This paper attempts a review concerning SiC-reinforced titanium, carbon and alumina-reinforced aluminium matrix composites. Main materials and processing routes developed currently for their production are described and some mechanical properties are compared.

2. Processing of titanium matrix composites

2.1. Fibres The reinforcement phase should possess high specific mechanical properties (modulus, tensile strength) up to 1000°C at least. Also, it should be both thermally and mechanically (expansion coefficient mismatch) stable with the titanium-based matrix. Table 1 shows the characteristics of main continuous fibres used in Ti–MMCs. It can be seen that there is a limited range of commercially available fibres. Most of them are large diameter SiC monofilaments produced by chemical vapour deposition (CVD). Silicon carbide offers the advantages of high strength at elevated temperature, good thermal stability and oxidation resistance. Two types of SiC fibres are produced: the ones

0921-5093/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved. PII: S 0 9 2 1 - 5 0 9 3 ( 9 8 ) 0 1 1 6 1 - 7

A. Vassel / Materials Science and Engineering A263 (1999) 305–313

306

Table 1 Characteristics of continuous fibres available for Ti-MMCs. Type

Name

Producer

Diameter (mm)

UTS (GPa)

Modulus (GPa)

SiC SiC SiC SiC Al2O3

SM 1140+ SCS-6 SCS-Ultra Trimarc Sapphire

DERA-Sigma Textron Textron ARC Saphikon Inc.

106 140 140 125 120

3.4 4 6.2 3.5 3.4

400 400 420 410 410

manufactured by Textron (SCS-6, SCS-Ultra) have a carbon core (33 mm in diameter) whereas those fabricated by DERA-Sigma (SM 1140+ ) and ARC (Trimarc) have a tungsten core (13 mm in diameter). Thermal stability of SiC fibres with a carbon core is superior to the ones with a tungsten core: silicon carbide reacts with tungsten above 1000°C with the formation W5Si3 and W2C and this reaction induces a decrease in the tensile properties of the monofilament [3]. All SiC fibres possess a protective coating to avoid any chemical interaction with the matrix during fabrication of the composite or service conditions. This coating mainly consists of carbon which has a thickness (3 to 5mm) and a structure varying with the fibre. The tensile strength of SiC monofilaments varies between 3.4 and 4 GPa generally (Table 1). However, a significant improvement has been obtained recently at Textron by modifying the CVD parameters for the deposition of SiC onto the carbon core and a tensile strength of 6.2 GPa has been reached [4]. Another type of reinforcement is the Al2O3 single crystal fibre produced by Saphikon Inc. (Table 1). It is interesting in the sense that it has high mechanical properties, excellent thermal stability and a coefficient of thermal expansion which is much closer to that of titanium-based alloys, by comparison with the one of silicon carbide. The fibre is supplied without an external coating and the chemical reactivity of alumina with titanium requires a protection [5,6]. Today, the high cost of the fibre hinders its use in Ti – MMCs.

Table 2 Main titanium-based alloys used as composite matrices Class

Name

b Ti-15-3 b b-21S a+b Ti-6-4 Near a Ti-6-2-4-2 Near a Ti-1100 Near a IMI 834 a2 Ti–24Al–11Nb O Ti–22Al–23Nb g Ti–48Al–2Cr–2Nb

Chemical composition (wt%) 15V–3Al–3Cr–3Sn 15Mo–2.7Nb–3Al–0.2Si 6Al–4V 6Al–2Sn–4Zr–2Mo–0.1Si 6Al–2.7Sn–4Zr–0.4Mo–0.45Si 5.8Al–4Sn–3.5Zr–0.7Nb–0.5Mo–0.35Si 14Al–21Nb 11Al–40Nb 33Al–2.6Cr–4.8Nb

2.2. Matrices The main titanium-based alloys used as matrices are reported in Table 2. They are listed according to their mechanical behaviour at elevated temperature, g titanium aluminides displaying the highest temperature capability. The most widely used titanium alloy in initial studies on Ti–MMCs is Ti-6-4. The advantage of b alloys over a+ b alloys is their better deformability which enables processing of the composites at lower temperatures. However, they exhibit a poor creep resistance which gives inadequate transverse properties of the composite for some applications. The increased operating temperature of new turbine engines requires matrices with improved high temperature properties and near-a alloys are of interest for that reason. Several compositions have been considered: Ti6-2-4-2, Ti-1100 and IMI 834. The best candidate appears to be Ti-6-2-4-2 although its creep performance is not as good as the one of the two other alloys. Indeed, matrix cracking has been observed in the as-consolidated condition in composites made with Ti-1100 and IMI 834 alloys [7,8]. It has been shown that this cracking phenomenon results from the combined effect of the microstructure of the alloy and thermal residual stresses at the fibre/matrix interface [9]. The first significant activity on titanium aluminide MMCs was performed on the SCS-6/Ti–24Al–11Nb system. The Ti–24Al–11Nb alloy is mainly composed of the a2 phase and it was shown that the properties of the composite are limited by the characteristics of that phase. These limitations include low ductility, chemical incompatibility with the carbon-rich coating of the SCS-6 fibre, poor creep resistance, inadequate transverse properties and environmental embrittlement when exposed to oxygen at elevated temperature [10,11]. Orthorhombic titanium aluminides containing the O phase represent the best alternative to a2 alloys at the present time. These new materials possess a better room temperature ductility and improved high temperature specific strengths (tensile, creep). The matrix compositions of interest range from Ti-(21 to 25)Al-(17 to 27)Nb. A comparative study conducted on SCS-6/Ti– 21Al–22Nb and SCS-6/Ti–24Al–11Nb systems re-

A. Vassel / Materials Science and Engineering A263 (1999) 305–313

Fig. 1. Schematic representation of the different fabrication processes for continuous fibre reinforced Ti–MMCs.

vealed that the orthorhombic matrix composite outperformed the a2 matrix composite in thermal stability, thermal fatigue and thermomechanical fatigue behaviour [12]. Titanium aluminide MMCs with a TiAl-based matrix have the potential to be used up to 800°C at least. However, attempts to fabricate SiC/Ti – 48Al – 2Cr–2Nb composites revealed an extensive cracking of the matrix in the as-consolidated condition which was due to its low ductility combined with high thermal residual stresses generated by the expansion coefficient mismatch of the two constituents. As stated above, alumina fibres seem more appropriate to be used as reinforcement in g titanium aluminides. Recently a double coating layer has been developed to protect the Saphikon fibre from its interaction with a TiAl-based matrix [13].

2.3. Fabrication routes The manufacture of bulk Ti – MMCs is difficult because of the high melting point and the extreme chemical reactivity of titanium-based alloys. Therefore, processing of composites is limited to solid state routes at a maximum temperature around 1000°C. Various fabrication methods have been developed with the objective of producing high quality and cost effective components. These methods differ in the way in which the fibre and the matrix are assembled before consolidation. The consolidation is performed in a temperature range where the matrix exhibits good formability, or even superplastic behaviour. The different routes are schematically illustrated in Fig. 1, and are usually termed as foil– fibre–foil, plasma spray coating and physical vapour deposition (PVD) coating. Details of these processes are described below.

2.3.1. Foil–fibre– foil This fabrication route consists of the consolidation of alternately stacked layers of alloy foil (80 – 120 mm thick)

307

and fibre mat made of aligned monofilaments (Fig. 1). The fibre mat is produced either by weaving with a wire or ribbon, or the fibres are held in place with a fugitive organic binder which is outgassed before the final consolidation [14,15]. This process can be only applied to titanium alloys that possess a good formability and that can be obtained in the form of foil at a reasonable cost, i.e. b, a+b and some near a alloys. Attempts have been made to produce titanium aluminide foil by chemical milling of sheet or pack rolling but these techniques are too expensive. Another disadvantage of this process is the rather poor fibre distribution and the existence of fibres touching which has a detrimental effect on mechanical properties, especially fatigue crack initiation. It should be mentioned that an alternative to the titanium alloy foil is the use of a powder matrix, whereby the powder is mixed with an organic binder and the resulting slurry is cast into a thin tape [1].

2.3.2. Plasma spray coating Vacuum plasma spraying is used to manufacture Ti–MMCs monotapes. Metallic powders of 20–100 mm are fed continuously into the plasma where they are melted and propelled at high velocity onto a single layer of fibres wound on a drum. The monotapes thus obtained are subsequently cut, stacked and hot pressed to form a fully dense Ti–MMC component (Fig. 1) [16,17]. The quality of the monotapes very much depends on the care that has been taken to avoid gas contamination (oxygen, nitrogen) and superficial fibre damage due to the impact of molten droplets. Fibre distribution of plasma sprayed MMCs is better than the one produced by the foil–fibre–foil process. 2.3.3. PVD coating The PVD processes have been recently developed and can be subdivided into two categories: electron beam evaporation and deposition (EBED) [18–20] and sputter techniques [21,22]. In both processes, SiC fibres are precoated with a thick layer of matrix before consolidation into a bulk composite (Fig. 1). The matrix material is provided entirely by the coating, thus avoiding the expensive alloy product forms such as foil or powder required for the aforementioned methods. The main advantage of these processes, as compared with other fabrication routes, is the attainment of a very uniform fibre distribution with no fibres touching. Furthermore, the fibre volume fraction (Vf) in the finished composite can be controlled by the thickness of the coating. Also, as each fibre is surrounded by matrix material, handling and consolidation are less damaging to the reinforcement than other processes. The EBED route involves the use of an electron beam (EB) gun to evaporate vapour from a titanium alloy rod which is then allowed to condense on the SiC fibre. The rate of evaporation depends on EB gun power, source

A. Vassel / Materials Science and Engineering A263 (1999) 305–313

308

which is good for a sputter technique but lower than the EBED process. Also, the metal utilisation efficiency is very high (\ 80%) due to the design of the apparatus. An example of a SCS-6/Ti-6-2-4-2 composite with a high Vf and an excellent fibre distribution, produced by the triode sputtering process, is illustrated in Fig. 2. A measure of the composite quality achieved during fabrication is to compare axial strength predicted by the rule of mixtures and experimental data. Room temperature tensile tests were performed on a SCS-6/Ti-6-4 composite (Vf= 33%); a mean ultimate tensile strength of 1820 MPa was obtained which is equal to 93% of the value calculated by the rule of mixtures (1960 MPa) [22]. This result reveals the advantage of the triode sputtering route which induces almost no damage to the reinforcement. Fig. 2. Transverse cross-section of a SCS-6/Ti-6-2-4-2 composite (Vf =67%) processed by triode sputtering [22].

3. Processing of aluminium matrix composites

3.1. Fibres temperature and vapour pressure of the element. In theory, the coating should have the same chemical composition as the evaporation source in a stationary regime. However, it appears that if the vapour pressures of alloying elements are very different, the composition of the coating on the fibre may be difficult to control with a single source. At present, only Ti-6-4 alloy can be deposited with success by this method. Work is in progress to deposit more complex alloy compositions such as Ti-6-2-4-2. An advantage of the EBED process is the high coating rate on the substrate (300 to 600 mm h − 1) but the metal utilisation efficiency, i.e. the percentage of the metal evaporated which is collected on the fibres, is low (10%) [19]. Among the different sputter techniques, the triode sputtering route has been developed at ONERA for the manufacture of Ti – MMCs [22]. As compared with the EBED route, it offers the possibility to use any matrix alloy with a precise control over the chemical composition of the coating on the fibre; different alloys such as Ti-6-4, Ti-6-2-4-2 and IMI 834 have been deposited with success. An important point is the level of interstitial contamination (oxygen, nitrogen) during the coating procedure. It has been shown that the gas contents of the target and the deposit are the same within the experimental scatter. The deposition rate is 20 mm h − 1

Initially, attempts to produce continuous fibre reinforced Al–MMCs were centred, as in the case of Ti– MMCs, on large diameter monofilaments (100 to 140 mm) such as boron or silicon carbide. However, owing to the high cost of these monofilaments and the low melting point of aluminium alloys which enables the fabrication of composites via a liquid route, small diameter fibres (B 15 mm) in the form of tows have emerged. Carbon and alumina are the main fibres used presently and their characteristics are listed in Table 3. There are two categories of carbon fibres depending on their mechanical properties: high strength (T800, M40J) and high modulus (FT700, KC139) fibres. It will be shown in the next section that they behave differently when they are incorporated in an aluminium matrix. Various alumina fibres have been investigated in the past to be used in Al–MMCs. In comparison, the Nextel 610 fibre developed recently by 3M allows a substantial increase in performance and can be produced at a relatively low cost. As compared with carbon fibres, the mean tensile strength of Nextel 610 is equivalent to the ones of FT700 and KC139 fibres but its modulus is much lower (Table 3). An advantage of alumina fibres over graphite fibres is the absence of

Table 3 Characteristics of continuous fibres available for Al–MMCs Type

Name

Producer

Diameter (mm)

UTS (GPa)

Modulus (Gpa)

C C C C Al2O3

T800 M40J FT700 KC139 Nextel 610

Toray Toray Tonen Mitsubishi 3M

5 5 10 9 10–12

5.5 4.4 3.3–3.8 3.8 2.8–3.5

290 380 700 750 400

A. Vassel / Materials Science and Engineering A263 (1999) 305–313 Table 4 Main aluminium alloys used as composite matrices Chemical composition (wt%) Al (pure) Al–2Cu Al–1Mg–0.6Si (6061) Al–4.5Cu Al–10Mg Al–7Si–0.6Mg (A357)

galvanic corrosion with aluminium alloys. In addition, they are chemically stable in the presence of molten aluminium.

3.2. Matrices The aluminium alloys used as matrices in recent studies on the development of continuous fibre reinforced Al–MMCs are reported in Table 4. Pure aluminium and low-addition alloys such as Al – 2Cu and Al–1Mg–0.6Si (6061) are used with the alumina Nextel 610 fibre [2]. More highly alloyed matrices (Al–4.5Cu, Al–10Mg and Al – 7Si – 0.6Mg) are employed with carbon fibres [23]. The advantage of highly alloyed matrices is their lower liquidus temperature as compared with aluminium; the gain is about 25°C in the case of Al–4.5Cu and Al – 10Mg, and 50°C for Al – 7Si–0.6Mg. In these conditions, the reaction kinetics between aluminium and carbon can be slowed down during processing of the composites so that the deleterious effect of interfacial reaction products on mechanical properties can be avoided.

309

misalignment of fibres), and the formation of reaction products at fibre/matrix interface is minimised. Owing to the poor wettability of carbon and alumina fibres by molten aluminium, a pressure must be applied to infiltrate a fibrous preform. It has been shown that a minimum pressure of 10 MPa is necessary to avoid infiltration defects [27]. High pressure casting (50–100 MPa), named as ‘squeeze casting’, can produce composites of very good quality with a simple shape [28]. However, this method is not adapted to components with a more complex geometry due to the possible deformation of the fibrous preform. Liquid infiltration under moderate pressure (10–20 MPa) eliminates the disadvantage of high pressure techniques and represents the emerging way to process Al–MMCs [2,29,30]. Fig. 4 gives an example of a KC139/Al–7Si–0.6Mg composite manufactured by this route.

4. Comparison of mechanical properties As opposed to silicon carbide fibres dedicated to Ti–MMCs that are produced with an external protective layer mainly composed of carbon, fibres used in Al–MMCs are supplied without any coating. It follows that the reactivity between fibre and matrix which controls mechanical properties depends on the chemical composition of the matrix in Ti–MMCs principally, when processing conditions are similar, whereas the fibre/matrix interaction in Al–MMCs is a function of more parameters such as the composition of the matrix, the reactivity of the fibre and the nature of the protective coating that may be applied on its surface.

3.3. Fabrication routes

4.1. Young’s modulus

The principal methods that are considered for the fabrication of continuous fibre reinforced Al–MMCs are schematically illustrated in Fig. 3. They involve either the production of preinfiltrated preforms prior to consolidation, or the liquid infiltration of a fibre preform. Preinfiltrated preforms can be wires, tapes or sheet that have had the metal introduced by liquid metal infiltration, thermal spraying by plasma gun, physical vapour deposition, electrodeposition, or a powder slurry [24,25]. Then, preforms are hot diffusion bonded to form the bulk composite. Liquid phase bonding is more appropriate than solid state bonding which may require the application of a high pressure (up to 100 MPa), and thereby can promote fibre breakage [26]. Casting techniques are very attractive for the manufacturing of continuous fibre reinforced Al–MMCs from an economic point of view. The difficulty is to infiltrate a fibrous preform such that an uniform distribution of fibres is obtained without defects (porosity,

The longitudinal Young’s modulus at room temperature of selected Ti–MMCs and Al–MMCs are compared with those of conventional monolithic materials in Fig. 5. The Young’s modulus of SCS-6/Ti-6-4 is 220 GPa (Vf= 35%) [31] and the one of Nextel 610/Al–2Cu is 240 GPa (Vf= 60%) [32]. It is to be noted that these values are two and three times the modulus of titanium and aluminium alloys respectively. High modulus carbon fibres in Al–MMCs promote an outstanding stiffness property: a value of 410 GPa has been obtained for a KC139/Al–7Si–0.6Mg composite (Vf=55%) [33]. The benefit of Al–MMCs over Ti–MMCs would be still more important on a density-corrected basis.

4.2. Tensile beha6iour It is now well recognised that the interface mechanical properties have a pronounced effect on the mechanical behaviour of metal matrix composites. Strong interfaces lead to moderate longitudinal and good

310

A. Vassel / Materials Science and Engineering A263 (1999) 305–313

Fig. 3. Manufacturing routes for continuous fibre reinforced Al – MMCs.

transverse strengths, while weak interfaces produce high longitudinal strength, close to the one predicted by the rule of mixtures, but with reduced transverse strength. The weak interface also gives improved fracture toughness and fatigue resistance.

4.2.1. Longitudinal strength The influence of fibre coatings on the longitudinal tensile strength of Al – MMCs at room temperature is illustrated in Fig. 6. Different types of fibres (alumina, carbon) and matrices (6061, Al – 4.5Cu, Al – 10Mg) are considered. In the absence of coating, alumina fibres such as Nextel 610 form a strong bond with aluminium alloys. In principle, if the matrix yield strength is sufficiently low (Al, Al – 2Cu), then matrix shearing at the fibre/matrix interface can act as a weak interface and the rupture strength is high [2]. With stronger alloys like 6061, the failure of a fibre propagates to adjacent fibres by growth of a coplanar crack and the tensile strength is rather low (Fig. 6). In order to obtain a

Fig. 4. Transverse cross-section of a KC139/Al–7Si–0.6Mg composite (Vf= 55%) processed by liquid infiltration under moderate pressure [30].

weak interface with 6061 alloy, the approach was to coat the alumina fibre and a concept of a thin C/TiB2 duplex coating was developed for that purpose [34]. The longitudinal tensile strength of a 6061 matrix reinforced with 40 vol.% coated alumina fibres is about 1100 MPa, close to the predicted theoretical strength (Fig. 6). The major problem with aluminium alloys reinforced with carbon fibres is the avoidance of the detrimental effect of the reaction between aluminium and carbon with the formation of Al4C3 during processing of the composite. The carbides at fibre/matrix interface are crack nucleation sites which lead to the premature failure of fibres. Typical examples of the low tensile strength of composites with the uncoated T800 carbon fibre are given in Fig. 6. It has been demonstrated that a pyrolytic carbon coating deposited onto the T800 fibre by low pressure chemical vapour deposition can act both as a diffusion barrier and a mechanical fuse [35–37]. The beneficial effect of this coating on the composite strength is illustrated in Fig. 6. Another interesting feature is the different behaviour of high resistance and high modulus carbon fibres. The latter ones, like KC139, are less reactive toward aluminium and as a consequence it does not appear necessary to apply a protective coating on the fibre (Fig. 6) [33]. An important benefit in incorporating continuous fibres in metal matrices is the improvement in high temperature strength. Recent data of the specific longitudinal tensile strength versus temperature of some Ti–MMCs and Al–MMCs are reported in Fig. 7. From a general point of view, Al–MMCs possess better specific strengths than Ti–MMCs up to 300°C. In particular, the KC139/Al–10Mg composite exhibits a very high strength at room temperature. As opposed to Al–MMCs, tensile strengths of Ti–MMCs decrease more slowly with temperature. It is also to be noted that SCS-6/Ti-15-3 and SCS-6/Ti-6-4 composites display equivalent properties when the temperature increases although Ti-15-3 alloy matrix is less temperature resistant than Ti-6-4. This last point

A. Vassel / Materials Science and Engineering A263 (1999) 305–313

311

Fig. 5. Longitudinal Young’s modulus: materials comparison at room temperature.

4.2.2. Trans6erse strength The room temperature transverse strengths of selected Ti–MMCs and Al – MMCs are reported in Table 5. The rupture strength of SCS-6/Ti-15-3 and SCS-6/Ti6-4 composites is only about half the value of the matrix alone and this is attributed to the weak fibre/ matrix bond. Debonding occurs either within the protective carbon coating of the SCS-6 fibre, or at the interface between carbon coating and the fibre/matrix reaction zone [38]. By comparison, Al – MMCs exhibit even lower transverse strengths, especially in the case of the carbon fibre reinforced composite (FT700/Al– 10Mg) which possesses a very weak fibre/matrix bond. The difference between carbon and alumina reinforced

Al–MMCs is due to the strong bond that alumina forms with aluminium alloys. It is also to be mentioned that solution or precipitation strengthening of the matrix has a beneficial effect; the transverse strength of the Al2O3/Al–2Cu composite is double that of a composite with a pure aluminium matrix.

5. Conclusion Owing to the high melting point of titanium and its extreme reactivity with most ceramics, reinforcements used in Ti–MMCs are large diameter SiC monofilaments and composites are processed via solid state routes. Three main fabrication methods have been developed (foil–fibre–foil, low pressure plasma spray, PVD coating); they differ in the way in which fibre and matrix are assembled before hot consolidation under vacuum. By contrast, the low melting point of aluminium alloys enables the fabrication of Al–MMCs via a liquid route using small diameter fibres (carbon, alumina) in

Table 5 Ultimate transverse strengths at room temperature of Ti–MMCs and Al–MMCs

Fig. 6. Influence of fibre coatings on the longitudinal tensile strength of Al – MMCs at room temperature. Coating on Al2O3 fibre: carbon+ TiB2. Coating on T800 fibre: carbon.

Composite

UTS (MPa)

r (g/cm3)

UTS/r (MPa/g/cm3)

Reference

SCS-6/Ti-15-3 SCS-6/Ti-6-4 Al2O3/Al Al2O3/Al–2Cu FT700/Al–10Mg

450 420 120 280 20

4.1 3.9 3.4 3.4 2.3

110 110 35 80 9

[31] [31] [32] [32] [39]

A. Vassel / Materials Science and Engineering A263 (1999) 305–313

312

Fig. 7. Density-corrected ultimate tensile strengths of Ti – MMCs and Al – MMCs as a function of temperature.

the form of tows, much less expensive than large diameter monofilaments. The infiltration process under moderate pressure (10 – 20 MPa) has proven to be the most viable for the fabrication of Al – MMCs components having complex geometries. With regard to mechanical properties, unidirectionally reinforced Ti – MMCs and Al – MMCs offer outstanding tensile characteristics (modulus, strength) in the longitudinal direction. Specific longitudinal strengths of Al–MMCs are higher than those of Ti– MMCs below 300°C. Carbon fibre reinforced Al– MMCs exhibit the best tensile properties in the temperature range 20 – 300°C. The disadvantage of unidirectional metal matrix composites lies in their low transverse properties, due to the weak fibre/matrix bond essentially. As the main application of unidirectional Ti – MMCs will be in future aero-engines, great care should be taken in the design of critical rotating components. With regard to Al–MMCs, the anisotropy of their tensile strengths is more pronounced than in Ti – MMCs. However, the problem of the low transverse strength in Al –MMCs can be alleviated by the use of cross-ply laminates.

Acknowledgements The author gratefully acknowledges Dr M. Rabinovitch for technical discussions on aluminium matrix composites.

References [1] P.J. Doorbar, The introduction of reinforced TMC material into

rotating machinery (to be published). [2] H.E. Deve, C. McCullough, J. Metals 47 (1995) 33–37. [3] A. Vassel, F. Pautonnier, M. Raffestin, ONERA Technical Report RT 15/3684 MY, 1993. [4] Textron Specialty Materials, Filament Properties Data Sheet, technical documentation, 1997. [5] M. Nathan, C.R. Anderson, J.S. Ahearn, Mat. Sci. Eng. A162 (1993) 107 – 113. [6] F. Brisset, Doctorate Thesis, University of Orsay, 1993. [7] D.B. Gundel, F.E. Wawner, Compos. Eng. 4 (1994) 47–65. [8] A. Vassel, F. Pautonnier, M. Raffestin, ONERA Technical Report RT 19/3684 MY, 1994. [9] A. Vassel, J. Microsc. 185 (1997) 303 – 309. [10] S.L. Draper, P.K. Brindley, M.V. Nathal, Met. Trans. A 23A (1992) 2541 – 2548. [11] D.B. Miracle, P.R. Smith, J.A. Graves, Intermetallic matrix composites III, MRS, Pittsburgh, PA, 1994, pp. 133–142. [12] P.R. Smith, J.A. Graves, C.G. Rhodes, Met. Mat. Trans. A 25A (1994) 1267 – 1283. [13] A. Brunet, Doctorate Thesis, University of Paris VI, 1998. [14] R. Pailler, P. Martineau, M. Lahaye, R. Naslain, Revue de Chimie Mine´rale (t. 18) (1981) 520 – 543. [15] P.R. Smith, F.H. Froes, J. Metals, March (1984) 19–26. [16] R.A. MacKay, P.K. Brindley, F.H. Froes, J. Metals, May (1991) 23 – 29. [17] Y.Y. Zhao, P.S. Grant, B. Cantor, J. Phys. IV 3 (1993) 1685– 1691. [18] C.M. Ward-Close, P.G. Partridge, J. Mat. Sci. 25 (1990) 4315– 4323. [19] P.G. Partridge, C.M. Ward-Close, Int. Mater. Rev. 38 (1993) 1 – 24. [20] C. McCullough, J. Storer, L.V. Berzins, Recent advances in titanium metal matrix composites, TMS, Warrendale, PA, 1995, pp. 259 – 273. [21] R. Leucht, H.J. Dudek, Mat. Sci. Eng. A188 (1994) 201–210. [22] A. Vassel, C. Indrigo, F. Pautonnier, Titanium’95 science and technology, vol. 3, The Institute of Metals, 1996, London, 1996, pp. 2739 – 2746. [23] M.H. Vidal-Se´tif, M. Rabinovitch, J.C. Daux., J.L. Raviart, J.C. Laizet, R. Me´vrel, Proceedings ICCM-10, Vol. 2 Woodhead Pub. Ltd, 1995, pp. 449 – 456. [24] L. Scheed, Doctorate Thesis, University of Orsay, 1992.

A. Vassel / Materials Science and Engineering A263 (1999) 305–313 [25] S. Pelletier, Doctorate Thesis, Ecole Nationale Supe´rieure des Mines de Paris, 1994. [26] S.J. Harris, Treatise on materials science and technology, vol. 31, Academic, NY, 1989, pp. 255–294. [27] A. Mortensen, J.A. Cornie, Met. Trans. A 18A (1987) 1160 – 1163. [28] X. Dumant, E. Beaugnon, G. Regazzoni, J. Metals, November (1989) 46 – 51. [29] J.C. Daux, Me´moire CNAM, 1991. [30] J. Pora, P. le Vacon, C. Carre, Proceedings ICCM-10, Woodhead Pub. Ltd, 2 (1995) 19–26. [31] Textron Specialty Materials, Continuous silicon carbide reinforced titanium for high temperature applications, technical documentation, 1989.

.

313

[32] 3M, Aluminum matrix composites: typical properties data sheet, technical documentation, 1996. [33] M. Rabinovitch, J.L. Raviart, J.C. Daux, M.H. Vidal-Se´tif, ONERA Technical Report RT 30/3659 MY, 1996. [34] C. McCullough, H.E. Deve, T.E. Channel, Mat. Sci. Eng. A189 (1994) 147 – 154. [35] P. Bertrand, Doctorate Thesis, University of Orsay, 1996. [36] P. Bertrand, M.H. Vidal-Se´tif, R. Me´vrel, J. Phys. IV C5 (1995) 769 – 776. [37] M. Rabinovitch et al., Proceedings ICCM-9, Madrid, 1993, pp. 683 – 690. [38] A. Vassel, R. Me´vrel, J.P. Favre, J.F. Stohr, Characterisation of fibre reinforced titanium matrix composites, AGARD Report 796, 1994, pp. 9 – 1 – 9 – 11. [39] N. Kerrouault, ONERA internal report, 1996