Microstructure Characteristic and Fatigue Damage Behaviors of 2060 Al-Li Alloy Thin Plate

Abstract

The microstructure characteristic, fatigue damage behaviours and evolution of microstructure during the fatigue testing of 2060 Al-Li alloy thin plate were studied by fatigue tester equipped with in-situ observation device, OM, EBSD, SEM and TEM. The results show that recrystallized grains with irregularity shape and large size are observed, the Goss and Cube texture are the mainly types, abundant of T1 with size of 50~60nm are found in grains. During axial loaded fatigue testing, a crack initiates from the edge of sample and extend into grain along the direction with maximum Schmid factor. When the crack reaches and crosses the first grain boundary, the extending direction deflects from 45° degree to perpendicular with loading direction, and propagates along this direction till the sample quickly fracture. A large size deformation region contains numerous slip strips around the crack tip during the initiation and extending process is observed. The dislocations cut across the T1 precipitates located in grains during deformation, and release the stress concentration on the crack tip. The fatigue crack extends across the grains with serrated shape can result from the big orientation difference of grains and easy screwed T1 precipitates.