Fatigue damage at room temperature in aluminium single crystals—III. Lattice rotation
- 30 September 1996
- journal article
- Published by Elsevier BV in Acta Materialia
- Vol. 44 (9), 3477-3488
- https://doi.org/10.1016/1359-6454(96)00026-2
Abstract
Lattice rotation was observed in different scales in aluminium single crystals fatigued in push-pull in air at room temperature, a constant shear stress amplitude 4 MPa, zero mean stress and frequency of 20 Hz. Using the channelling contrast technique in SEM, contrast of grey and dark bands consistent in dimensions with those of PSBs was observed on the surface sectioned parallel to the Burgers vector b in an Al single crystal after 1.2 × 106 cycles, suggesting that there was lattice misorientation (rotation or tilt) between PSBs and the matrix in the specimen. It might be caused by local net material movement due to irreversible slip or non-uniform deformation in PSBs. Lattice rotation (about 6°) always appeared between a macroband and the matrix relative to the normals of two perpendicular surfaces of the specimens, as a result of net irreversible slip in one direction of b in PSBs. Often more cracks were found in a positive macroband than a negative one. Deformation bands coarser than PSBs and smaller than macrobands were also found on the surface containing b by the scanning acoustic microscope. They deviated slightly from the direction of the PSBs and were probably formed to release the internal stresses between macrobands and the matrix due to macroband formation. The macroband effect is likely a general metallographic characteristic of unidirectional fatigue in planar-slip metal single crystals. The lattice rotation was probably one of the key factors controlling crack initiation and early propagation in the Al single crystals.Keywords
This publication has 17 references indexed in Scilit:
- Fatigue damage at room temperature in aluminium single crystals—II. TEMActa Materialia, 1996
- Fatigue damage in aluminum single crystals—I. On the surface containing the slip burgers vectorActa Metallurgica et Materialia, 1995
- Mixed mode crack mouth reflection in time-resolved acoustic microscopy of short fatigue cracks in single crystal aluminiumJournal of Physics D: Applied Physics, 1994
- Influence of non-geometric effect of PSB on crack initiation in aluminium single crystalActa Metallurgica et Materialia, 1990
- A quantitative acoustic microscope with multiple detection modesIEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 1989
- The long-range internal stress field in the dislocation wall structure of persistent slip bandsphysica status solidi (a), 1987
- Cyclic deformation of al-single crystals at low constant plastic strain amplitudesActa Metallurgica, 1987
- A model of extrusions and intrusions in fatigued metals I. Point-defect production and the growth of extrusionsPhilosophical Magazine A, 1981
- A multiple scattering transport theory for electronPhilosophical Magazine A, 1980
- The mobile dislocation density and length of slip lines in dispersion-hardened copper crystalsScripta Metallurgica, 1977