Nanostructure evolution and deformation of nanocrystallites in nanocrystalline (nc-) Ti(N,B)/amorphous (a -) (Ti B2, BN) thin films were investigated by high resolution transmission electron microscopy. The results indicated that the incorporation of B into TiN led to the formation of the nanocomposite that consists of nc-Ti(N,B) grains embedded in an amorphous matrix. Increasing B content accelerated not only the formation of more [200]-oriented grains but also the twining deformation in nanocrystallites. The deformation was enhanced with increasing B content, which was attributed to the decrease of grain size with increasing B content and the formation of nc-Ti(N,B) solid solution by dissolving B into the TiN lattice. © 2005 American Institute of Physics.