Abstract
Tensile and hardness tests were performed on the eutectoid Al-Zn alloy between -196°C and room temperature and fractured surface observation was made.
As generally known, the higher strain rate and the lower testing temperature resulted in the larger yield stress, 0.2% proof stress and ultimate tensile strength. The stress-strain curves, the fractured surface appearance, the ductility and the temperature dependence of the hardness showed the occurrence of the ductile-brittle transition between -80°C and -40°C. The transition temperature was defined more adequately by the intersection point of σm-T and σF-T curves than by that of σy-T and σF3-T curves.The fractography revealed that the fracture surface consisted of the quasi-leavage pattern at -196°C and of the dimple pattern at -80°C The mean diameter of the dimples was of the same order as the grain size.
