Abstract
The strain-rate sensitivity of the flow stress represents a crucial parameter for characterizing the deformation kinetics of a material. In this work a new method was developed and validated for determining the local strain-rate sensitivity of the flow stress at different plastic strains. The approach is based on spherical nanoindentation strain-rate jump tests during one deformation experiment. In the case of ultrafine-grained Al and ultrafine-grained Cu good agreement between this technique and macroscopic compression tests has been achieved. In contrast to this, individual spherical nanoindentation experiments at constant strain-rates resulted in unrealistically high strain-rate sensitivities for both materials because of drift influences. Microstructural investigations of the residual spherical imprints on ultrafine-grained Al and ultrafine-grained Cu revealed significant differences regarding the deformation structure. For ultrafine-grained Cu considerably less activity of grain boundary sliding has been observed compared to ultrafine-grained Al.
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01 June 2017
An Erratum to this paper has been published: https://doi.org/10.1557/jmr.2017.245
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ACKNOWLEDGMENTS
The authors gratefully acknowledge the funding of the German Research Council (DFG) which, within the framework of its “Excellence Initiative”, supports the cluster of excellence “Engineering of Advanced Materials” at the University of Erlangen-Nuremberg.
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Feldner, P., Merle, B. & Göken, M. Determination of the strain-rate sensitivity of ultrafine-grained materials by spherical nanoindentation. Journal of Materials Research 32, 1466–1473 (2017). https://doi.org/10.1557/jmr.2017.69
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DOI: https://doi.org/10.1557/jmr.2017.69