AGING CHARACTERISTICS, STRESS-CORROSION BEHAVIOR AND ROLE OF MG SEGREGATION AT GRAIN-BOUNDARY IN 7175-HIGH-STRENGTH AL-ALLOY

The aging characteristics, stress corrosion behaviour and chemical com position of grain boundary in 7175 high-strength Al alloy during long term aging process have been investigated by hardness measurement, con stant elongation rate testing (CERT) and energy spectroscopy analysis. The results indicate that double peaks in aged state feature the hard ness and strength of 7175 Al alloy. Although the intensity of double p eaks is almost equal, the stress corrosion resistance in the second pe ak-aged state is better than that of the first peak-aged state. The ef fects of Mg segregation on the binding energy of grain boundary have b een calculated by using free electron theory developed by the authors. The results show that Mg segregation plays a significant role in cont rolling stress corrosion susceptibility, which is consistent with the experimental results.