Instytut Podstawowych Problemów Techniki

Streszczenie:

Pure Zinc single crystal was examined with instrumented spherical indentation on the basal-oriented surface with different tips’ radii. Atomic force microscopy (AFM) and electron backscatter diffraction (EBSD) were used to investigate the topography and orientation changes within the imprint and the surrounding surface. Noticeable pop-ins were reproducible in the majority of tests. Contrary to the literature reports on zinc, plastic deformation was observed prior to the first pop-in, resulting in a hysteresis between loading and unloading curves. Therefore, pop-ins were associated not with the onset of plastic deformation but with slip deformation and contraction twinning because the twins were found inside and outside the imprint after pop-in event. Numerous cells with different orientations resulting from slip and twinning were revealed by EBSD analysis of the residual impressions. The external twins manifested as sink-in patterns. To illustrate the experimental observations, schemes for the evolution of the complex pile-up/sink-in pattern in terms of the parameters of the pop-in event and the increase of the load after the pop-in event have been proposed. Some novel aspects of Zinc nanoindentation were observed including pop-in bursts occurred during unloading process and detwinning properties after indentation. Finally, the difference between indentation results corresponding to two different tips, including the inverse size effect in the indentation phase prior to the pop-in event, was briefly discussed.

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