Investigation of in-situ synthesis of NbAl_3/Al_2O_3 nanocomposite by mechanical alloying and its formation mechanism

摘要

The present study was carried out to synthesize NbAl_3/Al_2O_3 intermetallic matrix nanocomposite by mechanical alloying (MA) using Nb_2O_5 and Al as raw materials. This nanocomposite was produced through a mechanochemical reaction between Nb_2O_5 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 Nb_2O_5 takes place in an explosive mode after about 450 min of milling time. The milled powder had a microstructure consisting of nanocrystalline NbAl_3 base adjacent to Al_2O_3 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 15h of milling time, average crystallite size of NbAl_3 and Al_2O_3 were about 8 and 13 nm, respectively. Heat treatment of powder mixture milled for 15 h showed a good thermal stability for this nanocomposite.