EFFECT OF HOLDING TIME ON THE PRODUCTION OF Nb-NbAl3 INTERMETALLIC COMPOSITES VIA ELECTRIC-CURRENT-ACTIVATED SINTERING

Abstract

A recently developed powder metallurgy processing technique - Electric Current Activated (Assisted) Sintering (ECAS) was employed to produce intermetallic Nb-NbAl3 composites. In this study, to produce Nb-NbAl3 in-situ intermetallic composites, Nb (99.8 % purity, less than 44 mu m) and Al (99.5 % purity, less than 44 mu m) elemental powders were mixed in the stoichiometric ratio corresponding to the Nb-Al phase diagram. The effect of different processing times, for (10, 30, 60) s, under maximum of 2000 A and 1.5-2.0 V, was investigated. Scanning electron microscopy and X-ray diffraction analysis were used to characterize the produced samples. X-ray diffraction studies revealed that the dominant phases are NbAl3 and Nb. Scanning electron microscopy examinations showed a dense microstructure with a very low amount of porosity and also a trace amount of residual aluminium. The microhardness of the test materials sintered for 60 s via electric-current-activated sintering was about 405 HV +/- 46 HV0,05.