Effect of Alloying with Copper on the Microstructure and Mechanical Properties of Al-30wt% Zn Alloy

A. F. Abd El-Rehim, M. M. El-Sayed, H. A. El-Sayed, M. Abd El-Hafez

This paper describes the microstructure and mechanical properties of a series of Al-Zn-Cu alloys ranging from 0 to 2 wt% Cu. Optical microscopy (OM) and X-ray diffraction patterns (XRD) were used for microstructural characterization, and creep tests for a preliminary assessment of mechanical properties. The results showed that the steady state creep rate, έ_st, of the ternary alloys decreased with increasing copper content up to 1 wt%, but above this level, it increased as the copper content increased. Furthermore, the results of the steady state creep indicated two deformation temperature regions (below and above 548 K). The energies activating the steady state creep were found to have the value of 39.2 kJ/mol in the low range of temperature (508-538 K) and 87.6 kJ/mol in the high range of temperature (558-557 K). The values of the activation energies in the first range of temperatures suggest the grain boundary sliding mechanisms while in the second range one it can be attributed to dislocation climb mechanism.