Paper number 738


O. Beffort1 S. Long1 and M.Diener2

1Swiss Federal Laboratories for Materials Testing and Research
Feuerwerkerstr. 39, CH-3602 Thun, Switzerland
2Institute of Metallurgy, Swiss Federal Institute of Technology
ETH-Zentrum, CH-8092 Zürich, Switzerland

Summary High quality hpAl/Altex and AlMg1/Altex MMCs were successfully produced by squeeze casting. The fatigue limit at R 0.1 is found to be 380 MPa, regardless of test temperature up to 250°C. Despite characteristic interfacial features and different mechanical properties, at R 0.1 no influence of the matrix chemistry on fatigue performance is noticed. At R -1 AlMg1/Altex shows a particular failure mode which is described as local fibre breakage in tension, followed by fibre crushing/kinking, matrix shear deformation and subsequent macro-buckling in compression; the fatigue limit is reduced by 50% compared to R 0.1. Sur-face damage from inadequate machining sensibly reduces the fatigue performance and leads to an increased scattering of the results. Monitoring of strain evolution during fatigue life proves to be an effective method to monitor damage development which may not be per-ceptible by the observation of the Young's modulus evolution on apparently intact specimens.
Keywords MMC, Al/Altex, fatigue, damage development, squeeze casting, continuous ceramic fibres, unidirectional reinforcement, machining.

Theme : Metal Matrix Composites ; Characterisation and Modelling

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