Charpy impact energy of nanocrystalline and polycrystalline cobalt

Charpy impact energy and microhardness of electrodeposited nanocrystalline cobalt (average grain size ∼18 nm), as well as electrowon polycrystalline cobalt in as-deposited (average grain size ∼1 μm) and annealed (average grain size ∼10 μm) conditions, were studied. At room temperature nanocrystalline, as-deposited and annealed polycrystalline cobalt had impact energies of about 2, 6 and 9 J, and hardness values of about 5, 3 and 2.5 GPa, respectively. Finer dimples were observed on the fracture surfaces of nanocrystalline cobalt in comparison with polycrystalline cobalt.