Effects of cold rolling and annealing time on fatigue resistance of AA5052 aluminum alloy

In the present study, the influences of cold rolling and annealing time on the fatigue crack propagation behavior of AA5052 aluminum alloy were investigated. The alloy sheet was cold-rolled under different rolling reductions, i.e., 0, 15, 30, and 45%. 45% as-rolled specimen was then annealed at 370°C under different annealing times, i.e., for 2, 4, and 6 h. The microstructure evolutions after the cold rolling and annealing treatments were also examined using optical microscopy whereas the fatigue crack propagation behavior was characterized by using a fatigue test. Results showed that severely elongated grains were observed with increasing the rolling reduction. The elongated microstructures were changed into equaxial structures due to recrystallization during annealing treatment. The fatigue life was decreased drastically by increasing the rolling reduction but increased significantly with increasing annealing time. The fatigue life of the alloy was reduced by 93% when cold-rolled up to 45%. On the other hand, the fatigue life of the 45% rolled samples was increased significantly by 412% when annealed at 370ºC for 6 h.