Amorphization of Ti/Cr multilayer films by solid-state reaction

Abstract

The solid-state reaction in Ti/Cr multilayered diffusion couples at temperatures between 450 and 650 "C was investigated by x-ray diffraction. It was found that an amorphous phase is formed at a concentration around 55 at. % Cr. The results are in excellent agreement with those obtained from mechanically alloyed powders, and with the corresponding metastable phase diagram calculated by the calculation of phase diagrams method. The observations strongly suggest that inverse melting is possible in the Ti-Cr system at around 55 at. % Cr.

Metastable Metallic Alloys

“…The amorphization transition was also noticed in Ti/Cr thin film interdiffusion couples with global composition around 55 at% Cr [4]. Sputter-deposited Nb±Cr films [12] are also comprised of an amorphous phase for 30 to 65 at% Cr, which delimitate its compositional range of stability at the ambient temperature of the substrates.…”

“…À the activation enthalpy for amorphous phase growth is generally lower than that required by the intermetallic stable compounds (3.8 versus 4.3 eV in Nb±Cr [7] and 2.3 versus 3 eV for Ti±Cr [4]). The amorphization enthalpy values are in rough agreement with those of Cr diffusion in b.b.c.…”

“…solid solutions (see also Fig. 1), as fully con- firmed by experiment [4]. The equilibrium compositions of the b.c.c.…”

“…or b.c.c. metastable solid solutions between early transition metals, prepared by this method: Ti±Cr [4,5], Nb±Cr [6], Zr±Mo and Ta±Cr [7], of which the Ti±Cr and Nb±Cr systems have been the most thoroughly investigated ones as yet.…”

“…1. a) Metastable phase diagram of the Ti±Cr system (calculated by the CALPHAD method (after [4])); b) equilibrium phase diagram of the Ti±Cr system (after [8]) peratures lower than the b.c.c. crystal field (Fig.…”