DETAILED PHASE-ANALYSIS OF A 77 AT.PERCENT-NB-AL SYSTEM PREPARED BY LOW-ENERGY BALL-MILLING

Elemental powders of Nb (77 at.%) and Al (23 at.%) were alloyed in a l ow-energy ball mill for 360-1800 ks in hopes of forming a nanocrystall ine intermetallic compound, Nb3Al. It was revealed by careful deconvol ution of XRD spectra into various peaks of possibly existing phases th at the resultant powder is a nanocrystalline multiphase mixture consis ting of Nb3Al, Nb2Al, elemental Nb and Al, with their particulate size s of approximately 5-8 nm, even after 1800 ks milling. The volume frac tions of these phases were estimated to be 28.4, 39.5, 30.3 and 1.8 vo l.%, respectively. The kinetic energy provided by ball-milling was ins ufficient to produce a single Nb3Al phase, and even heating to 933 K f or 25.2 ks failed the total conversion of a multiphase mixture.