The Elastic Constants of Copper Alloys

The elastic constants of single crystals of dilute solutions of Al, Si, Zn, Ga and Ge in Gu have been determined by the ultrasonic pulse method. Alloying causes a decrease in all the fundamental constants, C^, (C-^-C]^)^ and (G11 2C^2)/3> the relative decrease in (Gi2~Gi2)/2 being the greatest. The changes in shear constants Cu, and (C,-,-C-,2)/2 have been interpreted in terms of the known electrostatic and ionic contributions to these constants for copper,, The large decrease in (Cn-C^V^ is attributed to the change in ion-ion interactions upon alloying. The electrostatic shear stiffness of an alloy is found to be nearly equal to the electrostatic term for copper times the square of the electron atom ratio.