Effect of a decrease in sample dimensions on plasticity: application to the micro-forming of nickel

The mechanical behavior of polycrystalline nickel is investigated in tension as a function of the dimensions. Experimental tests and finite
element simulations with a crystalline plasticity code are carried out for samples with thicknesses ranging between 12.5 μm and 3.2 mm
and grain size around 100 μm. Results show three different kinds of behavior depending on the number of grains across the thickness due
to the apparition of stress and dislocation density gradients. Bulge tests are then used to study the formability of nickel polycrystals with
thickness lower than 400 μm.