Paper
Defect dependent dynamic nanoindentation hardness of copper up to 25 000 s-1
Authors
Hendrik Holz, Lalith Kumar Bhaskar, Tobias Brink, Dipali Sonowane, Gerhard Dehm, James P. Best, Rajaprakash Ramachandramoorthy
Abstract
Metals exhibit an upturn in strength at strain rates of approximately 1000 s-1 - 3000 s-1, governed by rapid dislocation multiplication, interactions and storage. This phenomenon is strongly influenced by the initial dislocation density before testing. However, the role of immobile dislocations arranged in low-angle grain boundaries (LAGBs) on deformation under such extreme conditions remains unexplored, despite their ubiquity in engineering materials. Here, we employ high strain rate nanoindentation targeted at an LAGB with tilt and twist components in copper crystals with different dislocation densities. We demonstrate that Taylor hardening remains valid over a wide range of strain rates. It was found that the influence of LAGBs on mechanical properties is within the scatter of the measurements. However, slip traces of indents close to the LAGB suggest that the LAGB acts as a barrier to dislocations. Molecular dynamics simulations further confirm these findings. The measured activation volume and low strain rate re-indentation onto indents performed at different higher strain rates give insights into the deformation mechanism. This work provides new insight into the interplay between microstructure and high strain rate deformation.
Metadata
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Raw Data (Debug)
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"raw_xml": "<entry>\n <id>http://arxiv.org/abs/2603.01845v1</id>\n <title>Defect dependent dynamic nanoindentation hardness of copper up to 25 000 s-1</title>\n <updated>2026-03-02T13:24:23Z</updated>\n <link href='https://arxiv.org/abs/2603.01845v1' rel='alternate' type='text/html'/>\n <link href='https://arxiv.org/pdf/2603.01845v1' rel='related' title='pdf' type='application/pdf'/>\n <summary>Metals exhibit an upturn in strength at strain rates of approximately 1000 s-1 - 3000 s-1, governed by rapid dislocation multiplication, interactions and storage. This phenomenon is strongly influenced by the initial dislocation density before testing. However, the role of immobile dislocations arranged in low-angle grain boundaries (LAGBs) on deformation under such extreme conditions remains unexplored, despite their ubiquity in engineering materials. Here, we employ high strain rate nanoindentation targeted at an LAGB with tilt and twist components in copper crystals with different dislocation densities. We demonstrate that Taylor hardening remains valid over a wide range of strain rates. It was found that the influence of LAGBs on mechanical properties is within the scatter of the measurements. However, slip traces of indents close to the LAGB suggest that the LAGB acts as a barrier to dislocations. Molecular dynamics simulations further confirm these findings. The measured activation volume and low strain rate re-indentation onto indents performed at different higher strain rates give insights into the deformation mechanism. This work provides new insight into the interplay between microstructure and high strain rate deformation.</summary>\n <category scheme='http://arxiv.org/schemas/atom' term='cond-mat.mtrl-sci'/>\n <published>2026-03-02T13:24:23Z</published>\n <arxiv:comment>31 pages, 7 main figures, 6 supplemental figure</arxiv:comment>\n <arxiv:primary_category term='cond-mat.mtrl-sci'/>\n <author>\n <name>Hendrik Holz</name>\n </author>\n <author>\n <name>Lalith Kumar Bhaskar</name>\n </author>\n <author>\n <name>Tobias Brink</name>\n </author>\n <author>\n <name>Dipali Sonowane</name>\n </author>\n <author>\n <name>Gerhard Dehm</name>\n </author>\n <author>\n <name>James P. Best</name>\n </author>\n <author>\n <name>Rajaprakash Ramachandramoorthy</name>\n </author>\n </entry>"
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