Microstructure and nanoindentation hardness of Ag/Fe multilayers

Ag/Fe multilayers with well compositional modulation periodicity of 4–60 nm were prepared at room temperature by evaporation deposition using an ultra high vacuum (UHV) chamber. Their microstructure and hardness were investigated using XRD, TEM and nanoindentation. The fcc/bcc type multilayers show a textured polycrystalline growth with Ag (111) and Fe (110) in Ag layers and Fe layers, respectively. The hardness increases with decreasing periodicity and approaches the maximum of 6.36 GPa at the periodicity of 4 nm. The peak hardness is 1.51 times mixture value. The experimental results are well explained by the dislocation-image force-based model developed by Lehoczky.