Creep behaviour of an Al–8.5Fe–1.3V–1.7Si–15SiC p composite at temperatures ranging from 873 to 948 K

Abstract

The creep behaviour of an Al–8.5Fe–1.3V–1.7Si alloy reinforced with 15 vol.% silicon carbide particles—an Al–8.5Fe–1.3Si–1.7Si–15SiC p composite—is investigated at four temperatures ranging from 873 to 948 K. The minimum creep strain rates ε ̇ m are measured using the isothermal constant stress creep test technique. The results indicate the true threshold stress σ TH decreasing with increasing temperature approximately linearly, the true stress exponent n is found equal to 2.5, the true activation energy of creep Δ H c close to the activation enthalpy of grain boundary diffusion Δ H B. For creep behaviour of the composite, very high values and very strong applied stress and temperature dependences of both the apparent activation energy Q c and the apparent stress exponent m c are found to be characteristic. These values of Q c and m c are interpreted in terms of the true threshold stress decreasing with increasing temperature. An attempt is made to account qualitatively for the origin of the true threshold stress in terms of behaviour of grain boundary dislocations and their interaction with particulates and particles located in grain boundaries.