STUDY OF FATIGUE DAMAGE IN 7010-ALUMINUM-ALLOY

Microscopic mechanisms controlling the fatigue damage in 7010 aluminum alloy are analysed. Cracks are initiated by the fracture of second-ph ase particles. Particles located in grains with a twisted cubic textur e have been observed as preferential damage sites. Cracks grow either along intergranular or transgranular paths both in recrystallized and unrecrystallized regions. The final rupture mechanism depends on the s tress level: at low and intermediate fatigue stress amplitudes the fai lure occurs by the unstable propagation of single cracks; at very larg e stresses multiple crack coalescence is observed. A model for the fat igue damage accumulation is presented. First a crack deviation model b ased on linear elasticity is described. It enables one to predict if c rack deviation is to occur when encountering a grain or subgrain bound ary. Finally, a fatigue life time model is developed in order to predi ct the cycle number to rupture and the qualitative influence of micros tructural parameters. Good agreement is observed between experimental and predicted results at intermediate fatigue stress amplitudes. (C) 1 998 Elsevier Science S.A. All rights reserved.