Microstructure Characterization of Electrodeposited Nickel Tested at High Strain Rates

A newly developed micro-kolsy bar system at the Army Research Laboratory has made it possible to test materials in compression at strain rates greater than 104 s−1. Opening up a new realm for testing of materials at high strain rates. In order to reach these high strain rates, sample diameters must be on the order of tens to hundreds of microns. Fabrication of these micro-samples is done using a femtosecond laser, since the ultrashort pulse width of this laser does not produce any appreciable damage layer. The high strain rate (103–105 s−1) behavior and resulting microstructure of electrodeposited nickel was investigated using this micro-kolsy bar system. The microstructure of the as-deposited and tested samples was examined with electron backscatter diffraction and transmission electron microscopy. Tested samples show evidence of dynamic recrystallization and formation of a large number fraction of high angle, Σ3 boundaries.