Effects of order on dispersion strengthening at high temperatures: A first model

Abstract

The creep strength of metallic materials can be improved significantly by the introduction of fine, non-shearable dispersoid particles. Over the last decade the theoretical understanding of this technologically important effect has been improved considerably; the results of these studies can be summarized as follows: (i) During the passage of a dislocation through an array of particles at high temperatures the Orowan stress is not reached because dislocation climb occurs. (ii) A more natural explanation for the effect is based on TEM observations which suggest an attractive particle-dislocation interaction. (iii) A more complete model which also considers the possibility of thermally activated dislocation detachment, results in a creep equation that has been successfully applied to several dispersion-strengthened materials. (iv) The model of detachment-controlled creep leads to several new consequences for optimum alloy design. The authors have presented a first model for the effect of superpartials on dispersoid-dislocation interactions relevant for creep strength of dispersion strengthened intermetallics. The analysis indicates that the particular size, relative to the spacing of the superpartials, can have a significant effect on the creep strength. This result suggests a connection between the APB energy and the optimum particle size in dispersion strengthened intermetallics.