Investigation of in-situ synthesis of NbAl3/Al2O3 nanocomposite by mechanical alloying and its formation mechanism

The present study was carried out to synthesize NbAl3/Al2O3 intermetallic matrix nanocomposite by mechanical alloying (MA) using Nb2O5 and Al as raw materials. This nanocomposite was produced through a mechanochemical reaction between Nb2O5 and Al. The structural changes of powder particles during mechanical alloying were studied by X-ray diffractometry and scanning electron microscopy techniques. It was found that the reaction between Al and Nb2O5 takes place in an explosive mode after about 450 min of milling time. The milled powder had a microstructure consisting of nanocrystalline NbAl3 base adjacent to Al2O3 particles with a nanoscale grain size. At longer milling times, no changes were observed, except peaks broadening due to the decreasing in crystallite size and increasing in lattice strain. After 15 h of milling time, average crystallite size of NbAl3 and Al2O3 were about 8 and 13 nm, respectively. Heat treatment of powder mixture milled for 15 h showed a good thermal stability for this nanocomposite.