TY - JOUR
T1 - Formation and crystallographic orientation study of quasicrystal, 2/1 and 1/1 approximants in Cd–Mg–Y system using electron backscatter diffraction (EBSD)
AU - Labib, Farid
AU - Ohhashi, Satoshi
AU - Tsai, An Pang
N1 - Funding Information:
The authors are grateful to Dr N.?Fujita at Tohoku University for reading the manuscript.
Publisher Copyright:
© 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group.
PY - 2019/6/18
Y1 - 2019/6/18
N2 - A partial isothermal ternary phase diagram of the Cd–Mg–Y system including icosahedral quasicrystal (i-QC) and 1/1 approximant (APP) was obtained at 673 K. The stability of the i-QC and APPs in terms of composition and temperature was studied, as a result of which the 2/1 APP phase was discovered at 773 K. Moreover, the i-QC phase was found to be stable at lower Y concentrations of ∼12–13 at.%, as compared to the 1/1 APP, which showed ∼15–16 at.% Y. Single i-QC, 2/1 and 1/1 APP grains were also synthesized applying centrifuging system. Electron backscatter diffraction (EBSD) characterization of the obtained i-QC and APPs revealed almost the same Kikuchi patterns for the i-QC and 2/1 APP, indicating high resemblance of their structures. However, the Kikuchi pattern acquired from the 1/1 APP was distinguishable from the one obtained from the i-QC as it showed split bands. The occurrence of the split bands was associated with significant deviation from a perfect icosahedral symmetry. This was also confirmed by analysing calculated electron diffraction and Kikuchi patterns along pseudo-five-fold axes of the 2/1 and 1/1 APPs. Finally, orientation relationships between the i-QC, 1/1 APP and α-Mg were investigated by analysing acquired EBSD Kikuchi patterns from the respective domains. Accordingly, three perpendicular two-fold axes of the i-QC and {100} axes of the 1/1 APP occur along three mutually orthogonal {0001}, {10-10} and {11-20} axes of the α-Mg.
AB - A partial isothermal ternary phase diagram of the Cd–Mg–Y system including icosahedral quasicrystal (i-QC) and 1/1 approximant (APP) was obtained at 673 K. The stability of the i-QC and APPs in terms of composition and temperature was studied, as a result of which the 2/1 APP phase was discovered at 773 K. Moreover, the i-QC phase was found to be stable at lower Y concentrations of ∼12–13 at.%, as compared to the 1/1 APP, which showed ∼15–16 at.% Y. Single i-QC, 2/1 and 1/1 APP grains were also synthesized applying centrifuging system. Electron backscatter diffraction (EBSD) characterization of the obtained i-QC and APPs revealed almost the same Kikuchi patterns for the i-QC and 2/1 APP, indicating high resemblance of their structures. However, the Kikuchi pattern acquired from the 1/1 APP was distinguishable from the one obtained from the i-QC as it showed split bands. The occurrence of the split bands was associated with significant deviation from a perfect icosahedral symmetry. This was also confirmed by analysing calculated electron diffraction and Kikuchi patterns along pseudo-five-fold axes of the 2/1 and 1/1 APPs. Finally, orientation relationships between the i-QC, 1/1 APP and α-Mg were investigated by analysing acquired EBSD Kikuchi patterns from the respective domains. Accordingly, three perpendicular two-fold axes of the i-QC and {100} axes of the 1/1 APP occur along three mutually orthogonal {0001}, {10-10} and {11-20} axes of the α-Mg.
KW - EBSD
KW - Quasicrystals
KW - approximants
KW - crystal growth
KW - magnesium alloys
KW - transmission electron microscopy
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U2 - 10.1080/14786435.2019.1585589
DO - 10.1080/14786435.2019.1585589
M3 - Article
AN - SCOPUS:85062483113
VL - 99
SP - 1528
EP - 1550
JO - Philosophical Magazine
JF - Philosophical Magazine
SN - 1478-6435
IS - 12
ER -