Solid state amorphization in the Co-Ti system

Application of a thermodynamic model (R. Benedictus, A. Bottger, E.J. Mitte meijer, Phys. Rev. B 54 (1996) 9109) shows that in the crystalline Go-cryst alline Ti system amorphization can occur both along the Co-Ti interface and along (high angle) grain boundaries in the Co and Ti sublayers. The model also predicts a preferred composition and a certain Limiting thickness for the amorphous product layer at the interface. These predictions are largely in agreement with experimental data obtained for Co-Ti multilayers at temp eratures in the range 523-583 K. A parabolic growth behaviour is observed f or the amorphous phase, suggesting diffusion controlled growth. The activat ion energy for the diffusion in the amorphous phase is (160 +/- 8) kJ/mol. Annealing the specimen for a relatively long time or at a relatively high t emperature, causes the amorphous phase to crystallize into an intermetallic phase with a CsCl-type structure and an average composition of Co40Ti60 Th e orientation relationship between the crystalline Co layers and the crysta lline Co40Ti60 phase was found to be Co(1 (1) over bar (1) over bar)//Co40T i60((1) over bar 10) and Co[110]//Co40Ti60[111] or Co[110]//Co40Ti60[001]. (C) 1999 Elsevier Science S.A. All rights reserved.