Mechanical properties of crystalline Cu/Zr and crystal–amorphous Cu/Cu–Zr multilayers

We compare the indentation hardness of crystal/crystal (C/C) Cu/Zr multilayers and the crystal/amorphous (C/A) Cu/Cu–Zr multilayers with equal individual layer thicknesses spanning from 1 to 200 nm. Both systems show similar layer thickness dependent evolution of hardness. At smaller layer thickness the C/C multilayers show softening, while no softening is observed in the C/A multilayers. The layer thickness dependent hardness is quantitatively estimated by using dislocation models. The significance of crystalline (Zr) layer and amorphous (Cu–Zr) layer on plastic deformation mechanisms is discussed.

► The C/C and C/A multilayers show the almost identical hardness at large h 5 nm.
► The C/A multilayers exhibit saturation hardness at small h < 5 nm.
► The C/C multilayers soften at small h < 5 nm.
► ACIs have a lower sliding resistance than that of CCIs.