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Figure 1
Schematic illustration of defects in single-component metal system produced by single-atom displacement. (a) frenkel pair in a crystal, (b) free volume like and anti-free volume like defects in an amorphous phase [1-5].
Figure 2
Schematic illustration of defects in multi-component amorphous alloy produced by single-atom displacement [5].
Under MeV electron irradiation, only single or, at most, double atom displacements of constituent elements can occur by the knock-on mechanism. Figure 1 shows a schematic illustration of the atomic defects in single-element crystalline and amorphous phases introduced by the electron knock-on effect. In the crystalline phases (a), not only a vacancy but also an interstitial is introduced under the irradiation, where the existence of an interstitial can be ignored in materials without irradiation. A vacancy type of a free volume like defect and an interstitial type of anti free volume like defect [1-4] are introduced in an amorphous phase under the irradiation (b). Figure 2 shows the schematic illustration of the defects in multi-component amorphous alloy. One can notice that many type defects can be considered in an amorphous phase. The concept of two-type defects is important for clarifying the mechanis of the irradiation induced crystallization of an amorphous phase.
REFERENCES
[1] T. Egami, K. Maeda, D. Srolovitz, V. Vitek.: J. Phys. 41, C8-272-C8-275 (1980)
[2] Y. Petrusenko, A. Bakai, V. Borysenko, A. Astakhov, D. Barankov, Intermetallics 17, 246-248 (2009).
[3] T. Nagase, T. Hosokawa, Y. Umakoshi: Intermetallics 18, 767-772 (2010), http://dx.doi.org/10.1016/j.intermet.2009.12.003
[4] T. Nagase, Y. Umakoshi: Intermetallics 18 1803-1808 (2010), http://dx.doi.org/10.1016/j.intermet.2010.02.044
[5] T. Nagase, Advanced materials design by irradiation of high energy particles, in: Progress in Advanced Structural and Functional Materials Design, Ed., T. Kakeshita, Springer, 2013. pp. 137-153., ISBN 978-4-431-54063-2, http://www.springer.com/materials/structural+materials/book/978-4-431-54063-2
