The interfacial reaction and microstructure in a ZK60-based hybrid composite

The oxidation behavior of B4C particles was investigated by measuring the weight changes during isothermal heating at 650 to 800 degrees C. The interfacial microstructure and fractography of the B4Cp and SiCw reinforced ZK60 magnesium hybrid composite was studied using a scanning electron microscope (SEM), a transmission electron microscope (TEM) and an electron energy loss spectrometer (EELS). It was found that the oxidation of B4C particles in air at the temperatures investigated produced an amorphous B2O3 surface layer. The oxidation kinetics was limited by the diffusion rate of oxygen through the liquid B2O3 layer. The oxidation layer was found to dominate the interfacial reaction, the microstructure and the mechanical properties of the hybrid composite. The rod-like MgB2 and the granular MgO were produced due to the reaction between the B2O3 and the magnesium matrix. The intimate bonding between the MgB2 and both the reinforcements and the matrix is believed to be the main reason for the improvement of the mechanical properties of the composite. (C) 2000 Kluwer Academic Publishers.