T. Zhai et al., FATIGUE DAMAGE IN ALUMINUM SINGLE-CRYSTALS .1. ON THE SURFACE CONTAINING THE SLIP BURGERS VECTOR, Acta metallurgica et materialia, 43(10), 1995, pp. 3813-3825
Citations number
28
Categorie Soggetti
Material Science","Metallurgy & Metallurigical Engineering
An aluminium single crystal with the axial direction of [25 (1) over b
ar] was fatigued in push-pull at the constant resolved shear stress am
plitude 4 MPa, frequency 20 Hz and room temperature. Microcracks, micr
ovoids, macrobands, extrusions and intrusions were observed on the sid
e-surface containing the Burgers vector b. Most microcracks were opene
d, and were within, but approximately perpendicular to, PSBs. Slip ste
ps were found in the extrusions and intrusions. There was net irrevers
ible slip in one direction in most PSBs. Some short cracks along the P
SBs on the side-surface were also observed at 5 x 10(6) cycles. These
observations indicate that, without the aid of the surface roughness o
f PSBs, cracks can still be nucleated, and that, apart from the notch
effect of a PSB, there are other factors controlling crack initiation
in single crystal aluminium. There may be an internal tensile stress e
xisting in a PSB in the direction of b, and a shear stress applied by
the specimen grips in the specimen due to the irreversible dip in one
direction in PSBs. These stresses and the applied stress are responsib
le for the formation of microcracks, microvoids, extrusions, intrusion
s and macrobands on the side-surface.