Hydrogen effects on an amorphous Fe-Si-B alloy
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I. INTRODUCTION
II. EXPERIMENTAL DETAILS
HYDROGEN interaction with amorphous alloys has been studied extensively due to both scientific and technological interest.[1] In the framework of a more comprehensive investigation of hydrogen interaction with amorphous and quasicrystalline Zr69.5Cu12Ni11Al7.5 alloys, hydrogen effects on amorphous Fe80B11Si9 were studied as well, for comparison.[2] As Fe80B11Si9 does not contain hydride-forming elements, the effect of chemical composition on hydrogen interaction with amorphous alloys may be estimated by comparing results for this alloy to results for an amorphous Zr69.5Cu12Ni11Al7.5 alloy. The Fe80B11Si9 alloy belongs to the group of amorphous alloys composed of late transition metals (LTM) and metalloids (M). The ratio LTM:M (atomic concentrations) in this group is usually 80:20. Bennett et al.[3] suggested that this ratio results from the filling of all large Bernal holes with the smaller and softer metalloid atoms to stabilize the random configuration. The aim of this article is to present results on hydrogen absorption in and desorption from an amorphous Fe80B11Si9 alloy. In addition, hydrogen effects on the microstructure, as well as the characteristics and mechanism of hydrogen embrittlement (HE) in this alloy, are discussed in detail. Finally, the effects of metalloids on hydrogen diffusion are briefly discussed, applying a new model to simulate the diffusion behavior of hydrogen in dilute amorphous Fe-H, Fe-Si-H, and Fe-B-H alloys, as described in detail elsewhere.[4] In a recent complementary article,[5] the authors applied laser-induced shock-wave measurements to determine the dominant mechanism of HE in an amorphous Fe80B11Si9 alloy and to estimate the effects of the high pressures involved in cathodic charging. Therefore, these results are not presented within the present article.
Ribbons (,25-mm thick) of amorphous Fe80B11Si9 were used for this research. The ribbons were produced by planarflow casting and were kindly supplied by AlliedSignal Inc. (Parsippany, NJ). It is well known that various surface phenomena may affect the interaction of hydrogen with materials. For amorphous alloys, crystalline phases were detected near the surface of the ribbon that had not been in contact with the rotating wheel during melt spinning.[6] Furthermore, surface-oxide layers were reported to hinder the desorption of hydrogen from an amorphous Zr69.5Cu12Ni11Al7.5 alloy.[7] Hence, Auger electron spectroscopy/X-ray photoelectron spectroscopy (AES/XPS) experiments were carried out in this research before hydrogen charging, in order to compare the chemical composition of both sides of the ribbon. The results indicated that both were slightly oxidized.[2] By means of optical microscopy, entrapped gas blisters were identified on the dull side. As others have observed as well,[8] this side had been in contact with the rotating wheel. Optical microscopy inspections, X-ray diffraction (XRD), and electrical resistivity measurements, performed following a preliminary series of cathodic
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