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High Temperature Materials

Glass and glass-ceramic matrix composites

This review reports about the most used glass matrices (2) and reinforcements (3) for the preparation of glass- and glass-ceramic composites, their preparation methods (4), their properties (5) and the foreseen applications (6) in the field of transports, aerospace and biomedical. In particular, the thermal and mechanical properties of glass- and glass-ceramic matrix composites are compared with those of the most common metals and ceramics. Finally, some comments are reported about the probable development of the research in this field of great technological importance (7).

Interfacial equilibria in Ti-particles/glass ceramic composites

Titanium particle-reinforced glass ceramic matrix composites were prepared by sintering under an Ar atmosphere titanium particles (Tip) and the glass powders 45ZnO-15PbO-40B2O3 (mol%) (ZPB) for the ZPBT composites and 48.8SiO2-48.8CaO-2.4B2O3 (SCB) for the SCBT composites. Each composite was characterized by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction and differential thermal analysis. In order to modify the interfacial strength of the composites, glass matrices with different amounts of TiO2 (TZPB and TSCB, 7 and 2.1 mol% TiO2, respectively) were prepared.

Calorimetric study on precipitation path in 2024 alloy and its SiC composite

Differential scanning calorimetry (DSC) is used in order to investigate the aging behaviour of AlCuMg alloys with different Cu:Mg ratios. Mechanism and kinetics of aging for these materials are compared with those of an (AlCuMg)-SiC composite. DSC results are in fairly good agreement with metastable AlCu and AlCuMg phase diagrams. The SiC reinforcement does not affect the precipitation path; furthermore, the activation energy for θ″ precipitation, calculated by Ozawa's method, is not appreciably different, taking into account the experimental error, for unreinforced alloy and composite.

Damage of 6061/SiCw composite by thermal cycling

The unreinforced 6061 alloy and a 6061/SiC composite, at the beginning in the T6 temper, were submitted to thermal cycling (up to 2000 cycles) in the temperature ranges 25-180°C and 25-220°C. The microstructure of these materials was studied by scanning electron microscopy and mercury intrusion porosimetry. Mechanical and thermomechanical properties were also investigated. Tensile strength, hardness, Charpy impact resistance, fracture toughness, density, specimen dimensions and thermal expansion were compared before and after thermal cycling.

Role of Al2O3 fibers (Saffil) in thermal treatment of 2014-Al2O3(f) composite

The effect of Al2O3 (Saffil) short fibers on the response of 2014-Al2O3(f) composite to thermal treatment was investigated. Composite samples were produced by squeeze casting starting from ceramic preforms of Saffil (13% vol. of fibers). Their behaviour was compared to that of 2014 unreinforced alloy fabricated by squeeze casting as well. The best process parameters suitable for solution of alloying elements were assessed by means of differential scanning calorimetry (DSC) and electron microprobe analysis (SEM-EDS).

Oxidation of FeCrAl alloy: influence of temperature and atmosphere on scale growth rate and mechanism

The oxidation behaviour of a FeCrAl alloy with little rare earth content (Y = 0.01 wt.%) was investigated. Specimens of this alloy were submitted to long-term oxidation treatments (up to 30 days) at 900 and 1200 °C, under gaseous atmospheres containing 21, 10 and 2 vol.% of O2. The weight gain for unit area was measured vs. oxidation time. The alumina scale growth was found to occur, at least during the first days of treatment, according to Wagner's parabolic law. Afterwards, the layer rate growth decreases down to that expected on the basis of this law.