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

This letter reveals the dislocation arrangements characterization of deform ation bands (denoted DBII) in a copper single crystal fatigued at a high st rain amplitude gamma(pl) = 8 X 10(-3). The results show that the surface de formation morphology of the crystal displays the following features. (1) Pr imary slip bands (SBs) were formed after 2 x 10(4) cycles and these carried a relatively homogeneous and small plastic strain. (3) Secondary slip band s did not operate during cyclic deformation. (3) Deformation bands (DBs) wi th a width of 50 mu m 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 b e 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 d irection, which have not been reported previously. By crystallographic anal ysis of the DBII, it is shown that the habit plane of the DBII should corre spond to the ((1) over bar 01) plane. Based on the observations above, it i s suggested that the formation of DBII should be attributed to the local re gularization of dislocation walls within primary slip bands.