On the influence of gaseous impurities in the amorphization reaction of some titanium-based alloys

Abstract

Some titanium-based alloys were examined by X-ray and neutron diffraction and differential scanning calorimetry (DSC) as part of a continuing research programme on amorphous alloys produced by mechanical alloying (MA). Large differences were found between the X-ray and neutron diffraction patterns on the same materials, which can be understood in terms of the relative visibilities of the alloy constituents for the two radiations. The neutron diffraction patterns provide unequivocal evidence that the alloys contain both amorphous and crystalline phases. A characteristic series of broad Bragg peaks was observed in the neutron diffraction patterns of amorphous CuTi, PdTi and AlTi alloys which was not evident when using X-rays. These peaks were identified with a mixed oxide-nitride Ti(O, N) impurity phase. DSC analysis of selected milling products revealed the transformation of the metastable phases. It also provided enthalpy data for a thermodynamic description of the milling process. These observations provide support to our previous findings on the significance of gaseous impurities of the parent metals in the MA process.