Investigation on the atomic structural evolution of as-prepared and annealed ZrCuAl metallic glasses
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Atomic structures of the Zr48Cu45Al7 as-prepared and annealed metallic glasses (MGs) were investigated by performing the reverse Monte Carlo simulation on the synchrotron radiation-based experiments. It was found that although the annealed sample remains completely amorphous, the volumes of the Al-centered clusters evidently expand, which is attributed to the relatively longer Al–Zr bonds. As a result, the role of Al atoms as the glue atoms to connect and fix the Zr- and Cu-centered large clusters is accordingly weakened, which leads to the ease of the rearrangement of atoms and clusters in the glass state. This study provides an insight into the microstructures of MGs, which extends understanding of the structural evolution in the glass alloys during annealing prior to the precipitation of nanocrystals.
I. INTRODUCTION
As a class of amorphous materials, the metallic glasses (MGs) have been attracting increasing interest in recent years because they possess scientific and engineering significance due to their unique properties.1,2 Unfortunately, these MGs have encountered a challenge to be widely used in engineering because of their limited casting size, unsolved problem about the glass-forming mechanism, expensive cost, and so on.1 However, it is found that the precipitation of nanocrystals in the amorphous alloys can improve their properties,3 such as the good soft magnetic property4 and high strength,5 which may extend their application as engineering materials. Therefore, vast efforts have been devoted to searching for the relationship between the amorphous/nanocrystal structure and their unique properties.6–10 So far, amorphous/nanocrystal composite materials can be prepared via the thermal synthesis,11 the mechanical processing,12 and the electron irradiation13 upon MGs. In particular, as a thermal synthesis method, annealing treatment was largely used to prepare these materials, which also is available for probing the phase transformation kinetics and mechanism of the nanocrystallization in amorphous alloys.14–16 Whereas, the structural evolution of amorphous-to-nanocrystallization change is far from being clarified, especially whether and how structural evolution occurs in the glasses during annealing prior to the precipitation of nanocrystals is a long-standing issue.17 In this work, a series of state-of-the-art synchrotron radiationbased experiments coupled with simulations were performed to address this issue, by investigating the structural a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2012.14 1164
J. Mater. Res., Vol. 27, No. 8, Apr 28, 2012
evolution of the Zr48Cu45Al7 amorphous alloy,18 which is a representative bulk MG with unique engineering and structural significance. II. EXPERIMENTS AND SIMULATIONS
The Zr48Cu45Al7 alloy ingot was prepared by arc-melting the mixtures of Cu (99.9 wt%), Zr (99.9 wt%), and Al (99.9 wt%) elements in Ti-gettered high-purity argon atmosphere, which was melted at least five times to ensure its compositional homogeneity. The c
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