MICROSTRUCTURE DEPENDENCE OF YIELDING AND FRACTURE IN Cd- Zn ALLOYS M. S. Sakr, A. A. E|-Shazly, M. M. Mostafa, H. A. E1-Sayed Physics Department, Faculty of Education, Ain Shams University, Cairo, Egypt A. A. Mohamed Physics Department, Faculty of Science, Ain Shams University, Cairo, Egypt Received 11 October 1989; in revised form 9 January 1990 The coefficient of logarithmic work-hardening, the yield stress and the fracture stress of Cd-2 wt. % Zn alloy of different grain diameters and of Cd-17"4 wt. % Zn alloy decrease with increasing working temperature. Two relaxation temperature regions have been found, the low-temperature region of relaxation (below 483 K) and the high-temperature region (above 483 K). The fracture surface energy for Cd-2 wt. % Zn alloy has been calculated and found to be 1"2 J/m 2 at the two temperature regions of relaxation. X-ray investigations show that the residual internal strains in the deformed samples increase with increasing working temperature and exhibit a peak value at 483 K. I. Introduction Work-hardening theories on the basis of investigations of hexagonal metals have suggested that there is a similarity in the work-hardening mechanisms of hcp and fcc crystals [1-4]. These theories mainly attribute the work-hardening processes to the dislocations intersections. However, the theoretical considerations of Kirchner [5] of the temperature dependence of the work-hardening coefficient indicate that the point defects may play an important role in the work-hardening of hcp metals. In our previous paper [6] on transient creep during transformation in Cd-Zn alloys, it has been shown that the mechanisms controlling transient creep in the vicinity of transformation regions were grain boundary diffusion and volume dif- fusion in Cd. The aim of the present work is to investigate the effect of microstructure variations on the work-hardening parameters of Cd - 2 wt. % Zn and Cd - 17.4 wt. % Zn alloys during transformation. 2. Experimental details High-purity Cd and Zn (99"99%) were used to prepare Cd-2 wt. % Zn and Cd- 17.4 wt. % Zn alloys. The ingot was drawn to wires of diameter 1 mm. The Czech. J. Phys. 40 (1990) 1267