Materials Science Forum Vol. 678

Abstract: A study on low-cycle and high-cycle fatigue behaviour of 6061-Al₂O₃ composites reinforced with nominal volume fractions of 10% and 20% of Al₂O₃ particulates is presented. The effects of reinforcement geometrical features (volume fraction and size) and of the loading mode experienced during the different kind of fatigue tests (strain controlled and stress controlled tests) were evaluated. A relation with crack growth mechanisms was drawn by analyses on fracture surfaces and on longitudinal sections of specimens subjected to the fatigue tests. The micromechanisms of cyclic deformation and of microstructural damage acting in the materials are discussed and compared to data and observations available from the wide published literature.

Abstract: Composites made from compacted powders blends of Al with different Fe contents were produced and characterised with respect to mechanical and induction heating properties. Mechanical spectroscopy and hardness measurements were employed to follow the evolution of Young modulus and internal friction after ageing. It was found that above a critical iron content (>30% of the volume) a percolation network of Fe grains is obtained inside the specimen and the induction heating characteristics become comparable with those of ferritic steel samples.

Abstract: Titanium-metal-matrix composites (Ti-MMC) are materials with very large specific resistance and potential operative temperature up to 800° C. At present these composites are produced by Hot Isostatic Pressing (HIP), a reliable but expensive manufacturing method. To cut production costs, Centro Sviluppo Materiali SpA (CSM) has developed and patented an experimental plant for co-rolling at high temperature sheets of titanium alloy and silicon carbide monofilaments fabrics. The experimental Roll Diffusion Bonding (RDB) pilot plant permits a reduction of process costs of about 40% with respect to the HIP process. This work reports the results of microstructural and mechanical examinations carried out on composites realized by RDB and HIP. The comparison shows that the fibre-matrix interface is stable in both the composites while the mechanical properties of RDB composite are better due to its smaller grain size and high dislocation density.