| Summary: | Long range internal stress (LRIS) based mechanism and non-LRIS explanation regarding Bauschinger effect are in debate. LRIS is originated from dislocation pile-up and/or cell generated by the pre-loading, therefore dislocation structure characterization of pre-strained sample is critical to clarify this academic dispute. Dislocation structures in surface and bulk regions of pure Ni deformed to a low strain level are characterized and compared in this work. Discrete dislocations are presented as expected in the bulk region of Ni, however, the main feature in its surface region is dislocation cell with average size of 1.2 μm. The result suggests that the promoted development of dislocation cellular pattern in near-surface region plays a critical role in the Bauschinger effect. It helps to clarify the mechanisms of Bauschinger effect and reconfirm the LRIS based mechanism.
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