Process and Microstructure of Al-6Mg-0.8Zn-0.5Mn-0.2Zr-0.2Er Alloy with High Strength and High Damage Tolerance

The tensile strength and fatigue crack propagation rate tests were carried out for cold rolled, warm rolled and full annealed A1-6Mg-0.8Zn-0.5Mn-0.2Zr-0.2Er alloy. The microstructure before fatigue test, the fatigue fracture and crack propagation path were observed by electron back-scattered diffraction (EBSD), transmission electron microscope (TEM) and scanning electron microscope (SEM) in order to analyze the effects of microstructure on tensile property and fatigue crack propagation rate. The results show that the fatigue crack propagation rate of the warm rolled alloy with high strength is much slower than that of the cold rolled. The microstructure characterization shows that the warm rolled alloy has more subgrain boundaries than the cold rolled and full annealed alloys due to dynamic recovery during warm rolling. This kind of microstructure can improve the yield strength and fatigue crack propagation resistance.