Abstract
Notch toughness and fracture characteristics of Al-Mg-Zn alloys and their welds were studied by mea-suring the notched and unnotched tensile properties, Charpy impact value, crack propagation energy in a modified Navy tear test and fracture stress in a deep-notch test.
With increasing Mg content or with decreasing Zn content in the alloys with Mg+Zn≈6% (constant), ductility and toughness tended to increase, whereas strength tended to decrease. Al-4.5%Mg-1.5%Zn alloy was superior to 5083 alloy in ductility as well as strength.
Al-4%Mg-2%Zn alloy with comparable ductility to 5083 alloy was superior in strength to Al-4.5%Mg-1.5%Zn alloy, while both alloys were inferior to 5083 alloy in toughness evaluated by Charpy impact value and crack propagation energy in the tear test.
However, Al-Mg-Zn (Mg>Zn) alloy welds showed comparatively stable fracture with little reduction of fracture stress in the deep-notch test at cryogenic temperature, while the dimple pattern disappeared and intergranular cracking was observed in fractography with lowering the testing temperature.
