Deformation in Metallic Glasses Studied by Synchrotron X-Ray Diffraction

Abstract

Abstract:High mechanical strength is one of the superior properties of metallic glasses which render them promising as a structural material. However, understanding the process of mechanical deformation in strongly disordered matter, such as metallic glass, is exceedingly difficult because even an effort to describe the structure qualitatively is hampered by the absence of crystalline periodicity. In spite of such challenges, we demonstrate that high-energy synchrotron X-ray diffraction measurement under stress, using a two-dimensional detector coupled with the anisotropic pair-density function (PDF) analysis, has greatly facilitated the effort of unraveling complex atomic rearrangements involved in the elastic, anelastic, and plastic deformation of metallic glasses. Even though PDF only provides information on the correlation between two atoms and not on many-body correlations, which are often necessary in elucidating various properties, by using stress as means of exciting the system we can garner rich information on the nature of the atomic structure and local atomic rearrangements during deformation in glasses.

On cryothermal cycling as a method for inducing structural changes in metallic glasses

“…In single-crystal nanowires, the high surface mobility of the constituent elements induced large anelasticity 27 . It was also found that elastostatic loading and creep experiments induced structural anisotropy in metallic glasses [28][29][30] . In the case of cryothermal cycling, plunging of the sample into a vessel of liquid nitrogen creates an immediate temperature gradient, which creates biaxial tension in the surface plane, initiating anelastic local flow.…”

Metals Challenged by Neutron and Synchrotron Radiation

“…As Bragg diffraction is a discrete Fourier series of an infinite periodic structure, the discrete points Q i forming the reciprocal lattice, and coefficients expressed by structure factors S i , amorphous disordered systems have to be treated in a continuous Fourier integral with a continuous scattering function S(Q). The back-transformation from an amorphous diffraction pattern leads to the pair distribution function or radial distribution function, as briefly introduced by Egami et al [14]. Similarly, electrons scatter from atoms and form diffraction patterns, which can be obtained by measuring the extended X-ray absorption fine structure, known as EXAFS.…”

“…Likewise, Egami et al [14] treat the atomic response of metallic glass to perturbations by a uniaxial mechanical load, breaking the symmetry of the system and extracting further information on the amorphous microstructure over length-scales. Non-affine atomic rearrangements below the yield stress have been found to be localized and reversible, leading to the abovementioned pseudo-elasticity.…”

Nanocrystallization of Metallic Glasses Followed by in situ Nuclear Forward Scattering of Synchrotron Radiation

“…The use of in situ characterization techniques is, however, still limited to diffraction of synchrotron radiation [11][12][13]. Recently, more sophisticated techniques of real-time in situ synchrotron X-ray tomographic microscopy [14] and combination of time-resolved X-ray photon correlation spectroscopy and high-energy XRD [15] were applied.…”