Double strengthening of copper by dissolved gold-atoms and by incoherent SiO2-particles: How do the two strengthening contributions superimpose?

Copper single crystals have been simultaneously strengthened by solved gold -atoms and by incoherent SiO2-particles. The critical resolved shear stress (CRSS) tau(s), of a binary copper-gold solid solution and the CRSS tau(t) of the same solid solution additionally strengthened by SiO2-particles have been measured in the temperature range 90-283 K. From the experimentally e stablished temperature dependences of tau(s) and tau(t) and from the theore tically known one of tau(p) ( = CRSS if the SiO2-particles are the only str engtheners present), the function tau(t) (tau(s),tau(p)) has been derived: tau(t) =(tau(s)(k) + tau(p)(k)) (l/k), with k approximate to 1.8. This resu lt is at variance with a linear relationship suggested earlier by Ebeling a nd Ashby [Phil. Mag. 13 (1966) 805]. The bearings of the present findings o n the evaluation of experimental data on dispersion strengthening are evide nt. (C) 2000 Acta Metallurgica, Inc. Published by Elsevier Science Ltd. All rights reserved.