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Amorphous materials; Chemical bonds; Cobalt; Combinatorial mathematics; Glass; Mechanical properties; Metallic glass; Metals; Stiffness; Topology; X ray diffraction, Combinatorial approach; Combinatorics; Concentration gradients; High energy x-ray diffraction; Hybridization; Mechanical property measurements; Metallic glass thin films; Short-range order analysis, Thin films
Abstract:
An efficient way to study the relationship between chemical composition and mechanical properties of thin films is to utilize the combinatorial approach, where spatially resolved mechanical property measurements are conducted along a concentration gradient. However, for thin film glasses many properties including the mechanical response are affected by chemical topology. Here a novel method is introduced which enables spatially resolved short range order analysis along concentration gradients of combinatorially synthesized metallic glass thin films. For this purpose a CoZrTaB metallic glass film of 3 μm thickness is deposited on a polyimide foil, which is investigated by high energy X-ray diffraction in transmission mode. Through the correlative chemistry-topology-stiffness investigation, we observe that an increase in metalloid concentration from 26.4 to 32.7 at and the associated formation of localized (hybridized) metal - metalloid bonds induce a 10 increase in stiffness. Concomitantly, along the same composition gradient, a metalloid-concentration-induced increase in first order metal - metal bond distances of 1 is observed, which infers itinerant (metallic) bond weakening. Hence, the metalloid concentration induced increase in hybridized bonding dominates the corresponding weakening of metallic bonds. © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.