ON THE INFLUENCE OF GASEOUS IMPURITIES IN THE AMORPHIZATION REACTION OF SOME TITANIUM-BASED ALLOYS

Some titanium-based alloys were examined by X-ray and neutron diffract ion and differential scanning calorimetry (DSC) as part of a continuin g research programme on amorphous alloys produced by mechanical alloyi ng (MA). Large differences were found between the X-ray and neutron di ffraction patterns on the same materials, which can be understood in t erms of the relative visibilities of the alloy constituents for the tw o radiations. The neutron diffraction patterns provide unequivocal evi dence that the alloys contain both amorphous and crystalline phases. A characteristic series of broad Bragg peaks was observed in the neutro n diffraction patterns of amorphous Cu-Ti, Pd-Ti and Al-Ti alloys whic h was not evident when using X-rays. These peaks were identified with a mixed oxide-nitride Ti(O, N) impurity phase. DSC analysis of selecte d milling products revealed the transformation of the metastable phase s. It also provided enthalpy data for a thermodynamic description of t he milling process. These observations provide support to our previous findings on the significance of gaseous impurities of the parent meta ls in the MA process.