Fatigue crack micromechanisms in ingot and powder metallurgy 7xxx aluminum alloys in air and vacuum

摘要: Abstract Fractographic analysis of fatigue crack growth in 7075-T651 ingot and MA-87 powder metallurgy aluminum alloys is combined with high resolution, dynamic observation tip deformation opening. It found that below the Paris regime, both moist air vacuum, does not proceed cycle-by-cycle, but incremental. Crack extension a two-stage process which produces striation, only after number cycles during blunts accumulates local strain damage near tip, followed by an increment “brittle” extension. The effect to reduce plasticity required for extension, hence blunting preceding Implications analytical models based on micromechanics are discussed.