The Effect of Temper, Grain Orientation, and Composition on the Fatigue Properties of Forged Aluminum-Lithium 2195 Alloy

摘要

The AA2195 alloy was designed for aerospace applications. Fatigue failures are among the major causes of aircraft failures. However, there exist limited studies on fatigue behavior of forged AA2195 alloy. Samples of AA2195 alloys were taken from an aircraft wheel and an open-die hand-forged billet. A total of 44 aircraft wheel samples and 67 hand-forged samples were tested. Aircraft wheel samples taken from the hub and tubewell were prepared in two tempers: T6 (peak aged) and T8 (cold worked and aged). The hand-forged samples were prepared in three temper conditions (T6, T8-4% strain, and T8-8% strain) and cut in the transverse (T) direction, short-transverse (S) direction and 45 degrees between these directions (ST45). The study revealed that T8 temper, while providing higher strength, showed longer fatigue life compared to T6 temper. The anisotropic behavior of AA2195 hand forgings showed the trend N-T > N-S > N-ST45. The forged aircraft wheels at different locations and tempers showed similar fatigue life at high stresses. At low stresses, different locations showed significant differences in fatigue lives. The reason may be related to the variance of manufacturing and thermomechanical processes experienced by different locations on a complex-shaped wheel. The AA2195 aircraft wheel samples were also compared with samples taken from a similar aircraft wheel but made of AA2014 alloy. The results revealed that the addition of lithium significantly improved fatigue life.