Numéro
J. Phys. Colloques
Volume 48, Numéro C3, Septembre 1987
4th International Aluminium Lithium Conference
Page(s) C3-753 - C3-759
DOI https://doi.org/10.1051/jphyscol:1987388
4th International Aluminium Lithium Conference

J. Phys. Colloques 48 (1987) C3-753-C3-759

DOI: 10.1051/jphyscol:1987388

EFFECT OF MICROSTRUCTURE ON HIGH CYCLE FATIGUE BEHAVIOR OF Al-Li BINARY ALLOY

Z. DI1, S. SAJI2 et S. HORI2

1  Graduate School, Osaka University, Yamadoka 2-1, suita 565, Osaka, Japan
2  Department of Materials Science and Engineering, Faculty of Engineering, Osaka University, Yamadoka 2-1, suita 565, Osaka, Japan


Abstract
Effects of microstructures obtained by the three kinds of thermomechanical treatments on high cycle fatigue behaviors in Al-1.8wt%Li alloy were investigated by means of optical and transmission electron microscopy. The three kinds of treatments were as follows : 1) solution treatment, 2) solution treatment-aging and 3) solution treatment-cold rolling-aging. The results obtained are summarized as follows : (1) Fatigue strength increases with age-hardening due to δ'-Al3Li precipitates. Fatigue cracks nucleate preferentially at the sharp or coarse slip bands and propagate mainly along them in the solution-treated specimens and the aged specimens. (2) Deformation bands perpendicular to the rolling direction are formed heterogeniously within the elongated grains of the cold-rolled specimens, and sub-structure shows many microbands and cells. Fatigue strength in the thermomechically-treated specimens is higher than those in the aged specimens. (3) Fatigue strength in the specimens with the deformation bands parallel to the axis of fatigue stress is higher than that in the specimens with deformation bands perpendicular to the axis. The deformation bands perpendicular to the axis of fatigue stress can be preferential nucleation sites and propagation paths of fatigue cracks. Microstructures consisting of disloction cell structure and δ'-particles alleviate the localized planar slip of dislocations and retard the initiation of fatigue cracks.