Mechanisms for nanocrystal formation in metallic glasses

Rate-dependent serrated flow and plastic deformation in Ti45Zr16Be20Cu10Ni9bulk amorphous alloy during nanoindentation

“…The existence of a short-range or medium-range order icosahedral or crystalline clustering [26][27][28][29] (not necessarily stable icosahedral quasicrystalline or stable crystals) in the as-cast amorphous state physically explains the preferences for the primary crystallization of icosahedral quasicrystals, as was reported in Zr-and Hf-based glass specimens [26,27], or of crystalline phase [28,29] during devitrification. Moreover, on the basis of other studies, it can be further argued that pre-existing clusters may vary in density and sizes in certain glass specimens [31][32][33][34]. Consequently, during continuous DSC scan, these clusters may be energetically and preferentially formed from rich clustering sites (which may still be amorphous) when the temperature approaches, but is still below, the glass transition temperature.…”

Crystallization Behavior and Control of Amorphous Alloys

“…The dimensions and morphologies of the crystallization products strongly depend on the transformation mechanism, which is closely related to the chemical composition of the amorphous phase and to the thermodynamic properties of the corresponding crystalline phase. The crystallization products could include crystalline solids (solid solution, intermetallics, and/or compounds) (Foley et al, 1997;Kelton et al, 2003;Lu, 1996;Sahu et al, 2010;Zhang, et al, 2003) or quasicrystalline (Murty et al, 2000). As the crystallization process upon annealing of an amorphous phase is much slower than during solidification of liquids, it is relatively easier to fundamentally investigate crystallization in amorphous phases than in liquids on the processes of nucleation and growth, in particular of nucleation kinetics difficult to study quantitatively in the liquid state.…”

“…Al 88 Ni 4 Y 8 , and Fe-based amorphous alloys, e.g. Fe 73.5 Si 13.5 B 9 Nb 3 Cu 1 (Finemet) (Hono et al, 1992), are typically primary crystallization (Foley, et al, 1997;Kelton, et al, 2003). The control of primary crystallization behaviors could lead to nanocrytallineamorphous composites with special mechanical or functional properties (see Section 5.1).…”

Phase separation and nanocrystallization in Al92Sm8metallic glass

“…Nanocrystallization of the Al-based glasses was previously attributed to heterogeneous nucleation [11], quenched-in nuclei [12] and a new type of homogeneous nucleation [13]. Phase separation in Al-Gd-La-Ni glass was reported with nanocrystal nucleating preferentially on the boundaries between the two phases [14,15]. However the results from 3D-atom probe for similar alloy system did not provide an evidence of the amorphous phase separation [16].…”