Orientations of nuclei during static recrystallization in a cold-rolled Mg-Zn-Gd alloy

doi:10.1016/j.jmst.2020.05.027

Abstract

Abstract:

The static recrystallization process of a cold-rolled Mg-Zn-Gd alloy was tracked by a quasi-in-situ electron backscatter diffraction method to investigate the orientations of nuclei. The results show that orientation distribution of nuclei is associated with nucleation mechanism. The continuous static recrystallization nuclei display similar orientations to the parent grains with TD orientation. Differently, discontinuous static recrystallization nuclei formed within the parent grains (TD-45° orientation) show random orientations and a variety of misorientation angles but preferred axes <$\overline {52}$73> or <$\overline {52}$70>. Interestingly, a special oriented nucleation is found. Discontinuous static recrystallization nuclei originated from boundaries of the parent grain (TD-70° orientation) show concentrated TD orientations in another side due to the preferred misorientation relationship 70° <11$\overline 2$0> (∑18b). It is speculated that these two special misorientation relationships are related to the dislocation type.

Key words: Mg alloys, Orientation, Nucleation, Quasi-in-situ EBSD, Static recrystallization

L.Y. Zhao, H. Yan, R.S. Chen, En-Hou Han. Orientations of nuclei during static recrystallization in a cold-rolled Mg-Zn-Gd alloy[J]. J. Mater. Sci. Technol., 2021, 60: 162-167.

Figures/Tables 4

Fig. 1. The quasi-in-situ formation of CSRX nuclei which have similar orientations to their parent grain: (a) the IPF map displaying formation process of CSRX nuclei N1-N2, (b) (0002) PF together with 3D structure of nuclei N1-N2 and the parent p1, p3, (c) the misorientation between N1-N2 and corresponding parent grain where misorientation axes marked as A1-A3, (d) A1-A3 indicated in the hcp coordinate system. (P, p, N and G represent the parent grain, small part of the parent, nucleus and pre-formed grains, respectively).

Fig. 2. The quasi-in-situ formation of IG-DSRX nuclei which have random orientations and misorientation angles but preferred misorientation axis around [$\overline {52}$73] or [$\overline {52}$70] with respect to the parent grain: (a) the IPF map displaying formation process of IG-DSRX nuclei N1-N10, (b) (0002) PF sheet together with 3D structure of nuclei N1-N10 and the parent grain P (including p1-p6), (c) the misorientation between N1-N10 and corresponding parent grain where misorientation axes marked as A1-A10, (d) A1-A10 indicated in the hcp coordinate system.

Fig. 3. The quasi-in-situ formation of GB-DSRX nuclei which have concentrated orientation and special misorientation relationship relative to the parent grain indicating ON tendency: (a) the IPF map displaying formation process of GB-DSRX nuclei N1-N5, (b) (0002) PF sheet together with 3D structure of nuclei N1-N5 and the parent p1, p4, (c) the misorientation angle and axis between N1-N5 and P together with the angle between the misorientation axes A1-A5 and reference axis [$\overline 2$110], (d) A1-A5 indicated in the hcp coordinate system, (e) the schematic displaying that the crystal of p4 rotates 71.23° around [$\overline 5$140] to form N1.

Fig. 4. The schematic of crystal rotation of nuclei with respect to the parent grain: (a-c) CSRX nuclei formed by rotating 30° around [0001], (d, e) IG-DSRX nuclei formed by rotating any angle around [7$\overline {25}$0] and [$\overline 5$7$\overline 2$3], (f) GB-DSRX nuclei formed by rotating 70.53° around [11$\overline 2$0]. The orange and grey 3D crystal structure represents the parent grain and nucleus, respectively.

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