Some critical experiments on the strain-rate sensitivity of nanocrystalline nickel

✍ Scribed by R Schwaiger; B Moser; M Dao; N Chollacoop; S Suresh

• Publisher: Elsevier Science
• Year: 2003
• Tongue: English
• Weight: 698 KB
• Volume: 51
• Category: Article
• ISSN: 1359-6454
• DOI: 10.1016/s1359-6454(03)00365-3

✦ Synopsis

Systematic experiments have been performed to investigate the rate sensitivity of deformation in fully dense nanocrystalline Ni using two different experimental techniques: depth-sensing indentation and tensile testing. Results from both types of tests reveal that the strain-rate sensitivity is a strong function of grain size. Specifically microcrystalline and ultra-fine crystalline pure Ni, with grain size range of Ͼ1 µm and 100-1000 nm, respectively, exhibit essentially rateindependent plastic flow over the range 3 × 10 Ϫ4 to 3 × 10 Ϫ1 s Ϫ1 , whereas nanocrystalline pure Ni with a grain size of approximately 40 nm, exhibits marked rate sensitivity over the same range. A simple computational model, predicated on the premise that a rate-sensitive grain-boundary affected zone exists, is shown to explain the observed effect of grain size on the rate-dependent plastic response.