Crystallization of an amorphous Cu 60Ti 40 alloy prepared by planar magnetron sputtering

Abstract

The crystallization path of an amorphous Cu 60Ti 40, alloy was studied using differential scanning calorimetry (DSQ), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The samples were Cu-Ti films≈ 10 μm in thickness prepared by magnetron sputter deposition onto rotating glass substrates. Two exothermic peaks were observed at 418° and 433°C, respectively, with no evidence of a glass transition. Observations from TEM and XRD at various stages of isochronal crystallization indicate that the initial amorphous structure transforms first to a metastable microcrystalline b.c.c. structure prior to formation of the ordered equilibrium Cu 3Ti 2 crystalline phase. The intermediate metastable structure is initially favored since it requires only topological ordering of the atoms into a simple unit cell, without significant diffusion, whereas the final ordered structure requires atom rearrangement over longer distances. The contrast of this sequence of events to that of a similar Cu-Zr alloy is discussed. Analysis of the fully crystallized alloy by convergent beam diffraction is consistent with a P4/nmm space group for the equilibrium phase.