THE TENSILE PROPERTIES OF A PARTICULATE-REINFORCED AL-ALLOY IN THE TEMPERATURE RANGE-196-300-DEGREES-C

The tensile properties of a particulate reinforced Al-Si-Mg alloy were determined in the temperature range - 196-300 degrees C. Microstructu ral coarsening of a peak aged (T61) material occurs at the higher temp eratures (i.e. 200 and 300 degrees C), which, together with the test t emperature, results in a considerable decrease in flow strength for bo th the composite and unreinforced alloy. However, the strengthening ra tio (i.e. the ratio of composite to matrix strength, sigma(c)/sigma(m) actually increases with temperature. This effect is also observed whe n investigating the influence of test temperature alone (i.e. a stable matrix microstructure over the full temperature range). These results suggest that the primary relaxation mechanisms are damage accumulatio n and relaxation by plastic deformation of the matrix. There is no evi dence of unrelaxed behaviour, even at - 196 degrees C, and the strain rate used during testing is likely to be too high to allow diffusional relaxation to be operative at the higher temperatures. Copyright (C) 1996 Canadian Institute of Mining and Metallurgy.