Temperature dependent strength analysis of short fiber reinforced Al-Si metal matrix composites

Metal matrix composites (MMCs) were produced by a pressure infiltration technique, using Saffil (delta-Al2O3) alumina short fiber preforms as the reinforcement, and the alloy Al-12 wt% Si (LM 13) as the matrix material. The matrix alloy and the composites were subjected to a standard T6 heat treatment and consequently tensile tested. The room temperature strength of the composites were seen to increase up to 15 vol.% fiber and then deviated sharply from the linear behavior and decrease continuously as the fiber volume increased. As the test temperature was raised. all composites showed excellent retention of strength up to 300 degrees C. Furthermore, the experimental results of tensile strength were compared to a modified rule of mixtures (ROM). The high temperature strength analysis showed that the strength of planar-randomly oriented short fiber reinforced material can be explained through combined effects of load transfer, dispersion strengthening, and dislocation strengthening. The reinforcement behavior of these type of composites is seen to be controlled by the elevated temperature properties of the matrix alloy. The theoretical tensile strength values, calculated with a temperature dependent modified rule of mixture equation, showed an excellent agreement with experimental data at room temperature and also at elevated temperatures of up to about 200 degrees C. (C) 1999 Elsevier Science S.A. All rights reserved.