Formation mechanism of NbSi2-Al2O3 nanocomposite subject to mechanical alloying

摘要

Silicide compounds such as NbSi2 have many desirable properties such as high melting point, high resistance to oxidation and suitable electrical conductivity. However, they have limited practical use because of low ductility. To overcome this limit, we produced NbSi2 based nanocomposite containing Alumina second phase by an exothermic reaction between Al and Nb2O5 in mechanical alloying of Al-Nb2O5-Si system. Structural and phase evolution throughout milling were investigated by using X-ray diffraction and microscopy methods. It followed that after 10 h of MA, the reaction between Al and niobium oxide began in a gradual mode and after around 40 h of milling; the reaction was successfully completed. The final product consisted of NbSi2 intermetallic compound and nanocrystalline Al2O3 with a grain size of 15 and 45 nm, respectively. Microhardness and fracture toughness of nanocomposite were also measured which are greater than NbSi2 intermetallic. As the result of this research we showed that high strength together with increased ductility could be gained in nanocomposite compounds.