Fatigue Resistance of 2219 Aluminum Alloy and its Welded Joints

The paper presents fatigue test results for 2219 aluminum alloy specimens, cut from a plate 40 mm in thickness, under symmetric and pulsating loading cycle. It is shown that at stresses for above the endurance limit, the fracture of specimens has a multi-site nature and starts from their surface. At stresses close to the endurance limit, the fatigue crack in the specimens fractured at a smaller number of loading cycles is initiated from their surface and at longer lives, from subsurface fracture initiation sites. This accounts for the significant scatter of data on the life of specimens near the endurance limit. Fatigue tests under zero-to-tension loading cycle showed that under the same heat treatment conditions, the endurance limit value of specimens made by resistance butt welding is close to that of specimens without weld and much higher than that of specimens with argon-arc weld. The fractographic investigations of the fracture of specimens with weld show that in both types of welding, the fatigue cracks propagate through pores in the weld or in the heat-affected zone.