Steady-state creep of a particulate SiC/6061 Al composite

Abstract

The creep behavior of a 10 vol.% silicon carbide particulate reinforced 6061 Al composite produced by powder metallurgy (PM) has been examined by creep tests in both tension and compression at 400°C. The tensile creep data covering minimum creep rates of the orders 10 −9 to 10 −4/s show an apparent stress exponent n app≈13, but a comparison with compressive creep data reveals that some high strain-rate data in tension are due to the transition to the tertiary stage. Analysis of the data is made only for the steady-state creep rate, together with that for an unreinforced PM 6061 Al alloy, by incorporating a threshold stress. This gives a stress exponent n=3 for the matrix alloy, whereas the composite data show such a trend that the n value gradually changes from 3 to 1 as the effective stress increases. A new method of steady-state creep data analysis is formulated by taking account of the interface-confined diffusional flow and thereby the finding above is reasonably assessed.