AL 12MASS% ZN ゴウキン ノ ヒロウ キョウド ニ オヨボス ビリョウ CU テンカ ノ エイキョウ

The fatigue strength under repetitive tensile stress and the age-hardening process were examined in the case of a small addition of copper to the Al-12mass%Zn alloy. The results obtained are summarized as follows. (1) In isothermal age-hardening curve the stationary hardness value of copperadded alloy was a little higher than that of the binary alloy, but the time to reach the value was longer. (2) A small addition of a copper did not alter the thickness of the soft surface layer. (3) A small addition of copper did not alter the fatigue strength. Accordingly the existence of the soft surface layer is considered to increase the fatigue strength of the copper-added alloy, too