Dislocation arrangements and crystallographic characterization of deformation band in fatigued copper single crystal

Abstract

This letter reveals the dislocation arrangements and crystallographic characterization of deformation bands (denoted DBII) in a copper single crystal fatigued at a high strain amplitude gammapl = 8 x 10-3. The results show that the surface deformation morphology of the crystal displays the following features. (1) Primary slip bands (SBs) were formed after 2 x 104 cycles and these carried a relatively homogeneous and small plastic strain. (2) Secondary slip bands did not operate during cyclic deformation. (3) Deformation bands (DBs) with a width of 50 mum were homogeneously distributed over the whole surface of the crystal and were perpendicular to the SBs. (4) Dislocation patterns within the SBs often consisted of irregular structures, which did not show a persistent feature. The results indicate that these SBs are not typical persistent slip bands (PSBs). (5) Within the DBII, the microstructure can be classified into two types. One type consists of regular 100% ladder-like parallel PSBs. The other type is full of dislocation walls parallel to DB direction, which have not been reported previously. By crystallographic analysis of the DBII, it is shown that the habit plane of the DBII should correspond to the (101) plane. Based on the observations above, it is suggested that the formation of DBII should be attributed to the local regularization of dislocation walls within primary slip bands.