Microstructure of Mg–Zn Matrix Composite Reinforced with Nano-SiC Prepared by Thixomolding

抄録

Thixomolding technology was successfully used to produce Mg–5 mass% Zn matrix composites reinforced with nano-SiC. The composites containing 5 mass% of SiC nano-particles were fabricated under pure Ar or Ar+CO₂ atmosphere. Microstructure characterization has been carried out by scanning and transmission electron microscopy methods. It was found that regardless of the gas used, the composites consisted of unmelted globular α(Mg) grains surrounded by small areas of a magnesium solid solution formed directly from liquid and a mixture of SiC and MgO. Reaction of CO₂ with liquid alloy during process leads to the in-situ formation of MgO nano-particles, which results in an increase in the amount of oxide particles and refinement of the microstructure compared to the composite produced in pure Ar. These microstructure changes increased the hardness to 70 HV.

Fig. 3 (a) TEM bright-field microstructure and (b) corresponding electron diffraction pattern obtained for Mg5Zn/SiC–Ar composite.