Phase Separation and Crystallization in Cu-Zr Metallic Glasses

Abstract

The structural behavior of rapidly quenched Cu-Zr amorphous alloys was analyzed. High energy X-ray diffraction patterns and atomic pair correlation functions exhibit monotonic changes with composition. The experimental results can be well described by a solid solution-like replacement of Cu and Zr atoms in the whole composition range. No indications are observed that would support the existence of phase separation in the supercooled liquid state of the binary Cu-Zr alloys. For Cu 60 Zr 30 Ti 10 and Cu 60 Zr 20 Ti 20 bulk metallic glasses the formation of ultrafine nanostructures are proven upon heating. The transformation starts below the glass transition temperature. Phase separation in Cu-Zr-Ti bulk metallic glasses is related to primary crystallization.

Structure of the glass-forming metallic liquids by ab-initio and classical molecular dynamics, a case study: Quenching the Cu60Ti20Zr20 alloy

“…Since these parameters fitted on the ordered solid cannot describe the structure of the liquid either, as shown above, both the high-and low-temperature limits suggest a possible problem with this parametrization. The puzzling point however is that the same parametrization predicts a total rdf g tot (r) in rather good agreement with the (unpublished) experimental data 75 shown in Ref. 41 ( figure (9)).…”

“…As expected, the resulting g tot (r) at 300 K (not shown here) is indeed in between the one obtained with the initial {a Another indication suggesting metastability of the state described by the data of Ref. 75 is the fact that the AIMD run quickly departs from configuration (3) (see also figure (7)). More experiments would thus be useful to ascertain the structure in amorphous states reached through different thermodynamic paths.…”

“…The parametrization with {a s i } -which is not validated by AIMD -might thus correspond to a metastable state close to the one reached in Ref. 75 (the path for these data 75 is likely the same as in Ref. 39, which does not show the rdf ).…”

“…75, and excluding artifacts, one possibility is that the experimental rdf s in figure (8) are different because they actually correspond to different amorphous states. This idea of some dependence on the thermodynamic path through which the amorphous state is reached is found for example in Refs.…”

Phase formation and thermal stability in Cu–Zr–Ti(Al) metallic glasses

“…In case of a homogenous element distribution rather long-range diffusion would be necessary to obtain the equilibrium phases. However, it is still disputed whether or not phase separation occurs in the Cu-Zr-based glassy alloys [55,56]. A detailed discussion of this aspect is beyond the scope of this paper.…”