Size dependent alloying and plastic deformation behaviors of Ti/Ni nano-multilayers

Abstract Proper modulation ratio ( η ) and modulation period is very critical for alloying of metallic multilayers. In this work, s ize dependent alloying and plastic deformation behaviors of Ti/Ni nano-multilayers have been investigated by nanoindentation. It is found that the multilayers deposited at 450 °C and annealed at 600 °C have fully alloyed. Phase compositions of the alloyed multilayers strongly depend on η and massive B2-NiTi phases spring up at η  = 1.7. Nanoindentation hardness of the alloyed multilayers reaches the maximum at η  = 1.7 and also shows modulation ratio dependence, which mainly results from conversion of phase compositions with changing η . Indentation depth dependent hardness agrees well with the model of geometrically necessary dislocations.