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The degradation mechanism of SiC(SCS-6)/Super α 2 composite due to the interfacial reaction was studied using single-fiber composite specimens fabricated by the sputtering method, heat treated at 1273 K for various times, and tensile tested at room temperature. The main results are summarized as follows. (1) The tensile strength was reduced with progress of interfacial reaction by the formed defects on the fiber surface, while the formation of the reaction layers in the matrix side was not the direct reason for the reduction. (2) From the fracture mechanical analysis of the experimentally observed relation of the size and shape of the surface defects to the fiber strength, the fracture toughness of the fiber employed in the present work was estimated to be 2 to 4 MPa ρm. (3) The change in distribution of strength of the reacted fiber with progressing reaction was simulated successfully by combining the Monte Carlo method with the Weibull distribution function for the strength of the unreacted fiber, the Gumbell distribution function for the maximum effective size of the surface defect of the reacted fiber, and the fracture mechanics.

In SiC-SCS-6-fibre-reinforced IMI834 alloys, a high thermal stability of tensile properties and of the fibre-matrix interface for temperatures up to 700 °C was reported. In the present paper, the interface of these composites is investigated by analytical transmission electron microscopy in the as-processed condition and after a thermal treatment at 700 °C for 2000 h and at 800 °C for 500 h. The interface in (SiC-SCS-6)-IMI834 composites consists of two layers: the TiC reaction zone with a thickness of about 0.4 μm and a layer of a (Ti, Zr)xSiy phase with a thickness of about ∼0.1 μm. The energy-dispersive electron beam analysis of the (Ti, Zr)xSiy layer results in a (Ti, Zr)2Si phase with a Ti-to-Zr ratio of approximately 1.4. Electron beam diffraction of the (Ti, Zr)xSiy layer identifies it as S2 silicides present in near-α alloys. The thermal stability of the interface in the (SiC-SCS-6)-IMI834 composites is ensured by the continuous coating of the (Ti, Zr)xSiy phase. This is the case for a thermal treatment at temperatures up to 700 °C for 2000 h. After the treatment at 800 °C for 500 h, the thickness of the TiC reaction zone is increased, gaps in the (Ti, Zr)xSiy layer appear, titanium carbide grows further into the titanium matrix and the thermal stability of the interface is lost.

Graded titanium boride coatings (gTiB coatings) were deposited on SiC-SCS-6 fibres. Composites with an IMI834 matrix were processed by fibre coating with matrix and hot isostatic pressing (HIPing) of matrix coated fibres. The thermal stability of the composites was investigated by the determination of the tensile and interface properties after a thermal treatment at 800 °C for up to 1000 h.

In many cases the tensile properties of fibers coated with matrix can give first leads to the properties of multifilament composites with the same matrix material. In the present investigation the authors compare the tensile test results of the monofilament composites with those of multifilament composites of the same matrix material. For the matrix different titanium alloys and titanium aluminides are used and the matrix ductility is varied by the oxygen content. Their results demonstrate that beside the interface the matrix ductility mainly determines the properties of the mono- and multifilament composites. In the present investigation SiC-SCS-6 fibers (Textron Inc.) were coated with different titanium alloys and titanium aluminides using magnetron sputtering.

The microstructure of the Ti-6Al-4V matrix in SiC-fibre reinforced composites is characterised using light microscopy and is correlated to the composite processing parameters. The microstructures are compared with those of thermally and thermomechanically treated Ti-6Al-4V specimens

The thermal stability of the interface in an SiC-fiber reinforced Ti6Al4V-alloy was investigated using analytical transmission electron microscopy. Composites processed by hiping were heat-treated in vacuum between 600 °C and 800 °C for several hundred hours. The structure of the interface was investigated by TEM, and the element concentration in and near the interface was measured using EDX-STEM and EELS. Experimental errors resulting from the sample preparation are discussed. Based on the structural and analytical investigations, the conclusion can be drawn that the interface is stable for application temperatures of up to about 600 °C.

One of the major future applications of titanium matrix composites is as a material for airplane turbine components, e.g., in the compressor. Service temperatures of up to 800 C will be involved. This application objective will only be reached when it will be possible to solve two major material problems: first, a matrix with sufficient ductility at room temperature and sufficient strength at service temperatures has to be found; and second, the problem of fiber/matrix reaction at application temperatures has to be solved. In composites with the high ductility IMI834 alloy (Ti-5.8Al-4.0Sn-3.5Zr-0.7Nb-0.5Mo-0.35Si-0.06C in wt. pct) as matrix, the optimal tensile properties can be exploited: the ultimate tensile strength and Young`s modulus values are in accordance with the prediction of the rule of mixtures, and an elongation at fracture of nearly 1.3 pct, typical of SiC fibers, is measured. It was shown that in SiC-SCS-6 fiber-reinforced IMI834 composites, these properties are achieved up to temperatures of 1,000 C. In the present study, results of the thermal stability of the SiC-SCS-6 fiber-reinforced IMI834 alloys are presented.

The tensile strength of monofilamentary weakly bonded SiC fiber/γ-TiAl intermetallic compound matrix composite, prepared by the sputtering method, was measured and analysed using a fracture mechanical technique. The main results are summarized as follows: (1) The fracture of TiAl occurred prior to that of fiber, resulting in formation of circumferential cracks on the fiber. Interfacial debonding occurred during tensile test, resulting in long pull-out of the fiber. (2) The strength of the fiber in the TiAl matrix was nearly the same as that of the bare fiber. (3) The fracture mechanical analysis showed that (i) the interfacial debonding grows unstably upon initiation and (ii) the stress distribution in the fiber in the cross-section, where the matrix is fractured, approaches to that of bare fiber with increasing debonded length. The reason why the fiber strength was maintained in spite of the formation of cracks on the fiber surface due to the premature fracture of the matrix was accounted for by the full...

The properties of SiC-fibre reinforced Ti-6Al-4V and Ti-IMI834 alloys processed by fibre coating with matrix and hot isostatic pressing are discussed. A variable fibre volume fraction between 0.2 and 0.6 is obtained with nearly ideal fibre distribution and a matrix with a small grain size. Three methods for matrix deposition were tested: electron beam physical vapour deposition, magnetron sputtering and random arc deposition. The strength and matrix ductility of the composites are influenced by the amount of oxygen incorporated into the matrix during matrix deposition on the fibre. For composites with a low oxygen content in the matrix the tensile strength and Young's modulus measured in the fibre direction are in agreement with the rule of mixtures. For composites with a high oxygen level in the matrix tensile strength is reduced by 20%. The high temperature tensile strength was measured for composites with the Ti-IMI834 alloy as matrix up to temperatures of 970 °C and values of 1800 MPa at 600 °C and 1500 MPa at 800 °C were obtained for a fibre volume fraction of 0.40.

From the beginning of aviation people have searched for lighter and stronger aircraft materials. The first generation of aircraft was mainly built of wood and fabric. But soon aluminium became an important structural material, especially after A. Wilm had discovered the age hardening capability of Al-Cu alloys in 1906. Nowadays high strength aluminium alloys are still the most important structural materials for aircraft and aerospace vehicles.

For the development of SiC-fibre reinforced titanium alloys MMC-suited processing techniques have to be designed, and the problem of fibre-matrix interface has to be solved. Hot pressing and hot isostatic pressing are thought to be promising processing techniques on a laboratory scale, using diffusion bonding as basic mechanism. The problem of interface reactions can be solved by applying protecting coatings based on carbon.

A hot isostatic pressing technique for processing simple-shaped parts of metal matrix composites on a laboratory scale is discussed. For reinforcing the Ti6A14V alloy, SiC-fibres (Textron/AVCO SCS-6) were used. The processing of tubes, rings and shafts is presented.

Es wird ein kurzer Uberblick uber Herstellung und Eigenschaften von SiC-faserverstarkten Ti 6 Al4 V-Verbundwerkstoffen gegeben. Um die durch Reaktionen im Grenzflachenbereich verursachte Schadigung der SiC-Fasern zu vermeiden, wurden TiC- und TiN-Schichten zwischen Faser und Matrix eingebracht und deren Einflus auf die Ausbildung der Reaktionszone untersucht. Zum Nachweis der Reaktionen zwischen Faser und Matrix wurden die Rontgen-Hochtemperatur-Diffraktometrie und Auger-Elektronen-Tiefenprofilanalyse eingesetzt. Durch Aufbringen von TiC- und TiN-Zwischenschichten konnen der Faserangriff und die Grenzflachenreaktionen nicht vollstandig verhindert werden. Bedingt durch die langsame Reaktionsgeschwindigkeit kann allerdings bei kurzen Haltezeiten (bis etwa < 1 h) die Ausbildung der schadlichen Titansilicide vermieden werden. Nach den bisher vorliegenden Ergebnissen liefert die Beschichtung der SiC-Fasern mit TiN, insbesondere aber mit TiC, positive Ansatze fur die Weiterentwicklung dieser Verbundwerkstoffe. SiC-Fiber Reinforced Ti 6 Al4 V Alloy: Effect of TiC and TiN Interlayers on the Reaction Zone. Processing and properties of SiC-fiber reinforced Ti 6 Al4 V alloys are briefly summarized. In order to avoid the degradation of the SiC-fibers caused by interfacial reactions, TiC and TiN interlayers were incorporated and their influence on the formation of the reaction zone was investigated. The reaction fiber-matrix was determinated by high temperature X-ray diffraction and Auger electron depth profiling. Coating with TiC and TiN cannot completely avoid fiber damage and interfacial reactions. However, due to the low reaction rate, at short process times (ca. < 1 h) the formation of titanium silicides can be prevented. Based on these results, the coating of the SiC-fibers by TiN, but especially TiC, gives positive aspects for further improving these composites.

In the course of a trial investigation, 162 patients with malignant tumour were treated in their home between November 1986 and August 1988. A team - consisting of doctor, nurse and psychologist - was the link between patient, family practitioner, tumour centre and social services in an integrated treatment regimen. Chemotherapy was performed at home in 64 patients, artificial parenteral or enteral nutrition in 22. Home treatment was undertaken in 23 patients in the endstage of their illness and in 49 patients after mutilating cancer operations. The complication rate of home treatment was only 0.5%. Rehospitalization became necessary in some, especially because of complications of the underlying disease, which required extension of the treatment. With this regimen patients were able to remain at home for 84% of required treatment time (7921 patient days).