Study on microstructure, texture and thermal properties of LPSO reinforced Mg-Zn-Y(-Gd) alloys

The microstructure, texture evolution and thermal properties of the as-cast and as-extruded Mg₉₂Zn₄Y₄ and Mg₉₂Zn₄Y₃Gd₁ alloys with long period stacking ordered (LPSO) structure phases have been investigated in details. The results show that the microstructures of the as-cast and as-extruded alloys mainly consist of α-Mg solid solution, the lamellar 14H-LPSO phase and the Mg₃Zn₃(Y,Gd)₂ (W) phase. The thermal properties of all the alloys increase slowly with the temperature increased from 25°C to 100°C. The thermal diffusivity and the thermal conductivity values of as-extruded Mg₉₂Zn₄Y₄ and Mg₉₂Zn₄Y₃Gd₁ alloys taken along the extrusion direction (ED) are 43.548 mm²·s^-1 and 146.394 W·m^-1·K^-1, 36.461 mm²·s^-1 and 125.343 W·m^-1·K^-1 at 298 K, respectively. However, in the same condition, the values of as-cast Mg₉₂Zn₄Y₄ and Mg₉₂Zn₄Y₃Gd₁ alloys are 30.261 mm²·s^-1 and 99.233 W·m^-1·K^-1, 26.097 mm²·s^-1 and 88.639 W·m^-1·K^-1, respectively. This suggests that the thermal properties of the LPSO-reinforced magnesium alloys can be significantly affected by texture. After the hot extrusion, the basal texture can form in α-Mg phase and the 14H-LPSO phase in the as-extruded alloys. That is to say, the super thermal properties of the as-extruded alloys taken along the ED are due to the acceleration of phonons and electrons movement on the (0002) basal plane. While, the texture randomization occurs in as-cast alloys which can hind- r the directional movement of phonons and electrons.