New observation on heating Ni-Al multilayers of 10 nm periodicity

Multilayers of Ni and Al of 10 nm periodicity have been sequentially deposited by RF sputtering. Only elemental Ni and Al were present in the as-deposited samples. No phase formation was detected until 673 K. For samples heated to 873 K, TEM studies reveal the presence of large grains of $Al_3Ni$ (confirmed with large systematic tilts) and equiaxed nanocrystals of $Al_3Ni$. In addition to the reflections from these two phases, the samples contain additional reflections with streaking from an additional phase. Imaging with these reflections reveals domains with probably strain modulations. Small elongated precipitates of $Al_3Ni$ are also occasionally present in the $Al_3Ni$ matrix. The origin of this complex microstructure is discussed