Comprehensive characterization of the structure of Zr-based metallic glasses

Structure of metallic glasses fascinates as the generic amorphous structural template for ubiquitous systems. Its specification necessitates determination of the complete hierarchical structure, starting from short-range-order (SRO) → medium-range-order (MRO) → bulk structure and free volume (FV) distribution. This link has largely remained elusive since previous investigations adopted one-technique-at-a-time approach, focusing on limited aspects of any one domain. Reconstruction of structure from experimental data inversion is non-unique for many of these techniques. As a result, complete and precise structural understanding of glass has not emerged yet. In this work, we demonstrate the first experimental pathway for reconstruction of the integrated structure, for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:msub><mml:mtext>Zr</mml:mtext> <mml:mn>67</mml:mn></mml:msub> <mml:msub><mml:mtext>Ni</mml:mtext> <mml:mn>33</mml:mn></mml:msub> </mml:mrow> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:msub><mml:mtext>Zr</mml:mtext> <mml:mn>52</mml:mn></mml:msub> <mml:msub><mml:mtext>Ti</mml:mtext> <mml:mn>6</mml:mn></mml:msub> <mml:msub><mml:mtext>Al</mml:mtext> <mml:mn>10</mml:mn></mml:msub> <mml:msub><mml:mtext>Cu</mml:mtext> <mml:mn>18</mml:mn></mml:msub> <mml:msub><mml:mtext>Ni</mml:mtext> <mml:mn>14</mml:mn></mml:msub> </mml:mrow> </mml:math> glasses. Our strategy engages diverse (× 7) multi-scale techniques [XAFS, 3D-APT, ABED/NBED, FEM, XRD, PAS, FHREM] on the same glass. This strategy complemented mutual limitations of techniques and corroborated common parameters to generate complete, self-consistent and precise parameters. Further, MRO domain size and inter-void separation were correlated to identify the presence of FV at MRO boundaries. This enabled the first experimental reconstruction of hierarchical subset: SRO → MRO → FV → bulk structure. The first ever image of intermediate region between MRO domains emerged from this link. We clarify that determination of all subsets is not our objective; the essence and novelty of this work lies in directing the pathway towards finite solution, in the most logical and unambiguous way.