A theoretical concept for the design of high-temperature materials by dual-scale particle strengthening

The creep behavior of dual scale particle strengthened (DSPS) metals containing particles of two different size scales, namely nanometer size dispersoids and reinforcements with typical dimensions in the micrometer to millimeter range, is analyzed theoretically. Based on the concept of thermally activated dislocation detachment from dispersoid particles as rate-controlling mechanism in dispersion hardened matrices, a new creep equation for this advanced material class is developed. Analysis of the model leads to the prediction that creep strength levels far superior to today's best dispersion or reinforcement strengthened high temperature materials can be achieved by using dispersion and reinforcement hardening in combination and following certain design guidelines, related to the selected particle parameters. In particular, it is shown that a volume fraction mis of about 3/4 reinforcements with about 1/4 dispersoids is ideal in many cases provided reinforcements with sufficient aspect ratio and size are selected. (C) 2000 Acta Metallurgica Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.