HRTEM and Electron Diffraction Images of Amorphous Metallic Glasses
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Figure 1686a shows a HRTEM and electron diffraction pattern of a thermally quenched  Zr70Al8Cu13.5Ni8.5 MG (metallic glass).  The diffraction pattern shows a diffusion halo, indicating the absence of precipitates with size larger than 3 nm. Moreover, the absence of any nanocrystalline phase in the diffraction pattern confirms that this material consists of only a purely glassy structure in amorphous phase. The HRTEM image further showing a highly disordered structure without any sign of nanocrystals or ordered clusters, confirms again the fully glass nature.

HRTEM and its electron diffraction pattern of an as-cast Zr70Al8Cu13.5Ni8.5 MG (metallic glass)

Figure 1686a. HRTEM and electron diffraction pattern of a thermally quenched  Zr70Al8Cu13.5Ni8.5 metallic glass. Adapted from [1]

Deng et al. [2] analyzed plastically deformed Zr55Al10Ni5Cu30 metallic glasses using SAED technique in TEM (see Figure 1686b). Although both the structures before and after plastic deformation process were in amorphous state, the diffraction pattern taken from the deformed specimen shows shrinkage (La/Lb = 0.87) and broadening of diffuse halo rings in the diffraction patterns. Those changes of the diffuse rings indicate the increase of interatomic spacing and/or free volume was induced by the deformation process.

SAED patterns of a Zr55Al10Ni5Cu30 metallic glass before (a) and after (b) plastic deformation

Figure 1686b. SAED patterns of a Zr55Al10Ni5Cu30 metallic glass before (a) and after (b) plastic deformation process. Adapted from [2]

Figure 1686c shows the microstructure of an Al87Ni7Cu3Ce3 amorphous alloy. In the HAADF-STEM (Z-contrast) image, some brightest spots in white circles represent heavy Ce atoms or its small clusters (Z=58), while some darkest areas in red circles represent fcc-Al (Z=13) nanostructures in the amorphous matrix. However, the HRTEM image does not present clearly the structures of fcc-Al nanocrystals.

(a) HAADF-STEM image and (b) HRTEM image of an Al87Ni7Cu3Ce3 amorphous alloy
(a) HAADF-STEM image and (b) HRTEM image of an Al87Ni7Cu3Ce3 amorphous alloy
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Figure 1686c. (a) HAADF-STEM image and (b) HRTEM image of an Al87Ni7Cu3Ce3 amorphous alloy. Adapted from [3]

 

 

 

 

 

 

 

 

[1] Y.H. Li, W. Zhang, C. Dong, J.B. Qiang, K. Yubuta, A. Makino, A. Inoue, Unusual compressive plasticity of a centimeter-diameter Zr-based bulk metallic glass with high Zr content, Journal of Alloys and Compounds 504S (2010) S2–S5.
[2] Deng Yu-Fu, Yang Fei, Yang Jian-Lin, and Zhang Wei, The increasing of localized free volume in bulk metallic glass under uniaxial compression, Chinese Physics, 16(7), (2007) 2051.
[3] Eiji Abe, Atomic-Scale Characterization of Nanostructured Metallic Materials by HAADF/Z-contrast STEM, Materials Transactions, 44(10), 2035-2041, (2003).

 

 

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