Influence of Hole Cold Expansion on Microstructure and Fatigue Life of 2124 Aluminum Alloy

The change of fatigue life and microstructure of 2124-T851 thick plate after cold expanded with different deformation was studied by fatigue test, TEM, SEM and X-ray diffraction apparatus. The results show that the fatigue life increases with the increase of expanded deformation until the maximum value is reached, and then decreased rapidly with the increase of expanded deformation. At 0.4 mm expanded deformation, fatigue life reach peak value, which is 12.66 times of the non-cold-worked specimens. The microstructure research results show that the residual compressive stress and dislocation cell structure form around the cold-worked holes during the cold expansion, and increase quickly with the expanded deformation. The strengthened layer retarded the fatigue crack growth rate. The appropriate cold expanded deformation can improve the surface roughness of hole, and retard the initiation of fatigue crack, consequently improving the whole fatigue life.