Mechanical response of nickel multicrystals for shear and tensile conditions at room temperature and 573 K

Abstract The critical dimension (e.g. thickness for sheet, diameter for cylindrical part) of small components used in a miniaturized system is often a crucial factor affecting the mechanical behavior and the forming process, since in such length scale ranges the grain size is comparative to the mechanical part dimension. To have a better understanding of the mechanical behavior of microsized metallic parts, the size effects in 500 μm thick samples of nickel sheet were studied in tensile and shear loading states. The modifications of the mechanical behavior due to different numbers of grains across the thickness were thoroughly investigated at room temperature and 573 K. New experimental results obtained by shear tests at high temperature revealed that the transition from polycrystalline to multicrystalline behavior is more pronounced in tensile loading than in shearing conditions and that different surface sample state is observed. It was demonstrated that the reduced stress level effect depends not only on the temperature, but also on the stress state. In addition, with a moderate increase in temperature, the surface effects leading to the multicrystalline behaviors became more predominant in tensile condition than in shearing condition.