Variation in Dislocation–Strengthening Factors of Cu–Zn Alloys with Solid–Solute Zinc Contents

Abstract

Solid–solute zinc in copper alloys has size effect for matrix copper element and decrease stacking fault energy. These characteristics affect strongly on the work hardening, which is proportional to square root of dislocation density. To elucidate the effect of solid–solute zinc in copper alloys on work hardening, we characterized dislocation evolution with an increase in zinc composition in copper alloys. Cu–Zn alloys with compositions of 0, 10, and 30 mass％ were tensile–deformed, and their dislocation density were evaluated by using X–ray diffraction line–profile analysis. The increase in dislocation density with tensile deformation, accompanying work hardening, was enhanced with the zinc composition. Solid–solute zinc, which has larger atomic radius than copper, retards the dislocation motion, so that dislocation generation complemented lower mobility of dislocations in higher zinc composition alloys. While dislocation multiplication became more distinct in higher zinc composition, the dislocation strengthening for unit length of dislocations became smaller with the zinc composition. Decrease in the stacking fault energy with zinc composition suppressed the dislocation cross–slip, and the frequency of dislocation intersection would be reduced. As a result, the effective dislocation density, which can act as the dislocation forest cutting, decreased.