PSI - Issue 2_B

Vladimir Oborin et al. / Procedia Structural Integrity 2 (2016) 1063–1070 Author name / Structural Integrity Procedia 00 (2016) 000–000

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4. Chemical analysis of the «fish-eye» zone The chemical composition of AMG6 alloy is determined by the Hitachi S3400 scanning electron microscope from the radiation spectrum of reflected electrons using the INCA module (Figure 5 and Table 2). As is evident from the scanning electron microscopy data, the distribution of the alloy elements is non-uniform.

Table 2. Chemical composition in Zone 2 of fracture surface shown in Figure 5. chemical element Weight % Na 1.16 Mg 42.42 Al K

49.01 2.15 2.71 2.55

Ca Ba

The emission spectrum has been investigated in three regions. It has been found that in the center of the «fish eye» zone, in the region 2, the content of Mg and Al is 49% and 42%, respectively. In the region 1 adjacent to the «fish-eye» zone the content of Al and Mg is 91% and 6%, respectively, as it must be for AMG6 alloy. In the region 3 at the bottom of the «fish-eye» zone the content of Al and Mg is 72% and 24%, respectively.

(a) (b) Fig. 5. (a) The patterns of fracture surface (scaled- up fragment of the «fisheye» zone and (b) the total spectrum of reflected electrons in the region 2 obtained by the scanning electron microscope Hitachi S3400. The effects of ascending diffusion or elastic aftereffect (known as the Gorskii’s effect) by Shanyavskiy (2013). Well known are the inelasticity effects, which show themselves in the interstitial solid solutions with a specimen centered cubic lattice. In such a lattice (e.g., Al), an interstitial atom (e.g., Mg) is creative of anisotropic distortion. Having this atom shifted into a neighboring interstice will alter the vector of the largest distortion. Therefore, an extrinsically applied force will favor diffusion of the interstitials towards some ordered distribution and, hence, will produce respective inelastic deformation. During cycling (loading/unloading), amount of irreversible strain (stress relaxation) increases with time. Apparently, during low-strain cycling, storing of the lattice defects (growth of material damage) inevitably occurs as long as reversion of the above atomic recombination remains persistently incomplete; the additional inelastic strain, brought in by the irreversible part of the said atomic recombination, increases accordingly. Each of the single atomic displacements alters only a little the material state; therefore, a long-time cycling (large number of loading cycles) is