Loading rate sensitivity of nanoindentation creep in polycrystalline Ni films
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Nanoindentation creep tests in Ni thin films with 3,000 nm thickness were performed with different loading times (5, 10, 20, 30, and 50 s) under the holding load 5,000 μN and holding time 30 s to investigate the dependence of the indentation creep behavior on the loading rate. The results show that significant indentation loading rate sensitivity on stress exponent and hardness was found, which shows that the stress exponent increases with indentation loading rate. In contrast, the elastic modulus decreases slightly (more or less 1%) due to a longer loading time. Based on the experimental results, we infer that the creep phenomena observed were probably induced by plasticity.
KeywordsStress Exponent Transient Creep Indentation Creep Double Logarithmic Plot Carbon Steel Sheet
This work was financially supported by the National Nature Science Foundation (NNSF) of China (No. 10702057, 10772157 and 50531060), Fok Ying Tong Education Foundation (No.104014), and National Science Found for Distinguished Young Scholars of China (10525211).