Transformation between Nanocrystalline and Amorphous Phases in Zr-X Alloys during Accumulative Roll Bonding

Recent progress in metallic glasses in Taiwan

“…The diffraction spots and rings in the TEM diffraction patterns of the ARB specimens are all originated from the pure elements, meaning that the nanocrystalline phases are those unmixed hard particles left from the previous severe deformation and diffusion processes. A critical size of the nanocrystalline phases around 3 nm is consistently observed in all binary, ternary, and pentanary Zr-X based alloys, below the critical size a sudden transformation from the nanocrystalline to amorphous state would occur [50][51][52][53][54], as shown in Fig. 7 [50].…”

“…After around 80-120 cycles, the alloys can be mostly transformed into the amorphous matrix, as shown in Fig. 5 [49]. Note that the volume fractions of the remaining nanocrystalline phases and the interdiffusion-induced amorphous matrix can be controlled by the applied ARB cycle, as depicted in Fig.…”

“…The amorphous materials have also been prepared by accumulative roll bonding (ARB) via room-temperature cold rolling in the solid state for alternating thin layers of various metals with a special arrangement of composition [49][50][51][52][53][54][55][56]. Binary Zr-Ti, Zr-Ni, Zr-Cu and Zr-Al, ternary Zr-Cu-Ni, quaternary Zr-Cu-Ni-Ti and pentanary Zr-Cu-Ni-Ti-Al systems were systematically explored.…”

On the latest stage of transformation from nanocrystalline to amorphous phases during ARB: Simulation and experiment

“…The nanocrystalline phase near the interface is around 2 nm with nearly sphere in shape and it seems to become unstable when the size is further refined to below 2 nm. Previous studies [6,8] have concluded that the pronounced increase in interfacial energy of the nanocrystalline phase lead to the transformation into the amorphous state, and interdiffusion across the phase boundary is the controlling atomic mechanism [14], as depicted in Fig. 1(b).…”

Cyclic transformation between nanocrystalline and amorphous phases in Zr based intermetallic alloys during ARB

“…Hence, the Zr 50 Ti 50 alloy was found to be more efficiently vitrified, as compared to Zr 50 Ni 50 . After 80e100 F&R cycles, only a few nanocrystalline phases with nearly spherical shape and average size w2 nm remain and are dispersed in the dominant Table 1 Parameters used in tight-binding potential function amorphous matrix [11]. The residual nanocrystalline phases seem to become unstable with the further ARB passes and sudden transformation from the nanocrystalline to fully amorphous state occurred upon subjecting to a few more ARB cycles.…”