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The growth of hexagonal columnar dendrite during directional solidification with respect to the multi-controlling parameters such as anisotropy, cooling rate, temperature gradient and orientation angle were investigated by a quantitative phase-field method, respectively. The simulation results show that the increase of anisotropy, cooling rate and temperature gradient can accelerate the solidification velocity of columnar dendrites. Among them, the cooling rate has the most significant effect on the solidification velocity of columnar dendrite. In contrast, the solidification velocity of columnar dendrite slows down with the increase of the orientation angle. Meanwhile, the primary dendrite spacing decreases with the increase of cooling rates and temperature gradient, and the primary dendrite arms are smooth. The primary dendrite spacing increases with the increase of anisotropy and orientation angle, which provides space for the development of secondary dendrite arms. In addition, the effects of cooling rate and temperature gradient on the solid volume fraction were also studied.

The synchrotron radiation technology is a powerful tool for characterisation of the microstructure of alloys because of its strong penetration, high resolution and non-destructiveness. Mg alloys are widely used in engineering due to their low density, high ratio strength and good casting properties. The application of synchrotron radiation techniques in characterising the microstructure in various Mg alloys has made incremental progress. The present review introduces the basic principles of synchrotron radiation techniques, and summarises recent advances in the application of these techniques in understanding the solidification microstructure, deformation behaviour, phase transformation mechanism, hydrogen storage capacity, long-period stacking ordered structure of Mg alloys. The perspective on the development and further application of synchrotron radiation technology for alloy research is also discussed.

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