Separated contribution of particles and matrix on the creep behavior of dispersion strengthened materials

The high temperature creep behavior of an extruded Al-8.5Fe-1.3V-1.7Si dispersion strengthened material has been studied by means of tensile tests. The fine microstructure consisted of a 27% volume fraction of dispersoids, of about 50 nm in diameter, homogeneously distributed in the matrix. The microstructure remained stable and fine after testing at high temperature. High apparent stress exponents, n(ap), of about 25 and high apparent activation energies, Q(ap), of about 400 kJ/mol were observed. These high values cannot satisfactorily be explained by the various models existent in the literature. A new creep equation has been developed which is a generalization of the conventional general slip creep equation but without the use of a threshold stress. This equation correctly describes the creep behavior of this material and the high values of Q(ap) and n(ap). (C) 1997 Acta Metallurgica Inc.