Change in environmental structure around Al in Zr60Ni25Al15 metallic glass upon crystallization studied by nuclear magnetic resonance

In order to investigate the structural evolution around Al, pulse NMR experiments were carried out on 27Al in the Zr60Ni25Al15 metallic glass and the related crystalline compound, Zr6NiAl2. Different chemical shift peaks were observed around 2750 and 3000 ppm in the as-quenched Zr60Ni25Al15 and crystalline compound, Zr6NiAl2, respectively. Considering that the capped triangular prism of Zr9Al3 is formed around Al in the Zr6NiAl2 crystal, chemical correlation pairs of Al–Zr and/or Al–Al are fairly faint while that of Al–Ni may be dominant instead in the as-quenched state. These results suggest an inhomogenous chemical bonding nature in the Zr60Ni25Al15 metallic glass. The resonant peaks around 3000 ppm, which were distinctive in the Zr6NiAl2 crystal, appeared and became stronger upon crystallization through the relaxed state. Thus, drastic change in the local atomic configuration around Al was confirmed so as to form the unlike chemical correlation pairs of Al–Zr upon crystallization. The high glass-forming ability of the Zr60Ni25Al15 metallic glass should be attributed to the difficulties of significant atomic redistribution of the constituents around Al.