Interface structure and its formation mechanism in Mg_2B_2O_5w/AZ91D magnesium matrix composite

Phases,changes of surface chemical state of the extracted Mg2B2O5 whiskers(Mg2B2O5w) and the interfacial structure of the Mg2B2O5 w reinforced magnesium composite were investigated by means of X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),scanning electron microscopy(SEM) and transmission electron microscopy(TEM),respectively.It is found that MgO and MgB2 phase are formed at the matrix-whisker interface during vacuum-gas pressure infiltration process,which results from the interfacial reaction between Mg2B2O5 w and Mg matrix.The crystallographic orientation relationship between the Mg2B2O5 whisker and the interfacial reaction products is found to be [010]Mg2B2O5w//[110]MgO and[110]MgO//[21 10]MgB2,and(202) Mg2B2O5w//(002) MgO and(002) MgO//(0001)MgB2,respectively.Although the interface between Mg2B2O5w and matrix is generally clean,the thickness of the interfacial layer is uneven and the interfacial bonding between Mg2B2O5 w and matrix may be not strong.To improve mechanical properties of the composite,surface treatment technique of Mg2B2O5 w needs therefore to be developed.