PRINCIPLES OF PARTICLE SELECTION FOR DISPERSION-STRENGTHENED COPPER

A new fundamental approach to the design of high strength, high therma l conductivity dispersion-strengthened copper alloys for applications in actively cooled structures is developed. This concept is based on a consideration of the basic principles of thermodynamics, kinetics and mechanical properties. The design requirements for these materials in clude a uniform distribution of fine particles for creep and fatigue r esistance. a high thermal conductivity thermodynamic and chemical stab ility at temperatures up to 1300 K, a small difference in the coeffici ents of thermal expansion between the particle and matrix, and low par ticle coarsening rates at the processing and service temperatures. The theory for creep of dispersion-strengthened metals developed by Rosle r and Arzt is used to predict the optimum particle size for a given se rvice temperature and to illustrate the need for a high interfacial en ergy. Resistance to coarsening leads to a requirement for low diffusiv ity and solubility of particle constituent elements in the matrix. Bas ed on the needs for a low difference in the coefficients of thermal ex pansion to minimize thermal-mechanical fatigue damage and low duffusiv ity and solubility of the constituent elements, several candidate cera mic phases are compared using a weighted property index scheme. The re sults of this quantitative comparison suggest that CeO2, MgO, CaO and possibly Y2O3 may be good candidates for the dispersed phase in a copp er matrix.