Electron back-scattering diffraction preliminary analysis of heterogeneous nuclei in magnesium alloy during solidification process under GPa high pressure

The effective heterogeneous nuclei in Mg-7.92 Zn-1.70 Y alloy during solidification process under high pressure was investigated by EBSD. It is found that the orientation relationship between Mg matrix and MgY phase, [111]_（MgY）//[1210]_（α-Mg） and（101）_（MgY）//（0001）_（α-Mg）, exists between Mg matrix and MgY phase.The MgY phase is the potential heterogeneous nuclei substrate for a-Mg solidified under high pressure. It is calculated by Bramfitt mode that the mismatch between Mg matrix and MgY phase is greater than 12% under atmospheric pressure. When solidified under high pressure of 4 GPa, the solidification pressure can increase the number of the α-Mg nucleus by reducing the size of the nucleus, decreasing interfacial energy of MgY/a-Mg, and changing the wettability between MgY phase and α-Mg from non-wetting under atmospheric pressure to wetting under high pressure. The MgY phase becomes a powerful heterogeneous nuclei for α-Mg crystal. Increasing the number of valid heterogeneous nuclei substrate increases nucleus number and refines the grain of the alloy.