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 contai ning particles of two different size scales, namely nanometer size disperso ids and reinforcements with typical dimensions in the micrometer to millime ter range, is analyzed theoretically. Based on the concept of thermally act ivated dislocation detachment from dispersoid particles as rate-controlling mechanism in dispersion hardened matrices, a new creep equation for this a dvanced material class is developed. Analysis of the model leads to the pre diction 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 reinforceme nts with about 1/4 dispersoids is ideal in many cases provided reinforcemen ts with sufficient aspect ratio and size are selected. (C) 2000 Acta Metall urgica Metallurgica Inc. Published by Elsevier Science Ltd. All rights rese rved.