Influence of intermetallic particles on short fatigue crack initiation in AA2050-T8 and AA7050-T7451

Fatigue crack initiation at particles is studied in hot rolled 2050-T8 and 7050-T7451 material, using 1 to 4 mm cross section specimens. Both size and aspect ratio of particles are observed to affect their probability of being damaged. In 2050-T8 material, the probability that a matrix crack initiate at a cracked particle increases with its size, and no effect of aspect ratio is observed. In 2050-T8 specimens, matrix cracks initiate at both precracked (Al, Cu, Fe, Mn) particles and particles cracked during cycling. Initiation in 7050-T74 specimens occur on Mg2Si particles which may be cracked or debonded, and Al 7 Cu 2 Fe particles that are cracked during cyclic loading.