CARBIDE AND HYDRIDE FORMATION DURING MECHANICAL ALLOYING OF TITANIUM AND ALUMINUM WITH HEXANE

Mixtures of elemental titanium and aluminium powders of overall compos ition TixAl1+x(x=0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.75, 0.8) were mechani cally alloyed in a planetary-type ball mill. Hexane was added as a pro cess control agent to reduce powder agglomeration during milling. The as-milled powders were characterized using X-ray diffraction, differen tial scanning calorimetry, scanning electron microscopy and transmissi on electron microscopy. During milling, the hexane is partially dissoc iated, with the free carbon and hydrogen incorporated within the TixAl 1-x allay powders in increasing amounts with increasing milling time. The amount of incorporated carbon increases with the initial Ti conten t of the powder mixture, reaching a maximum of 12 wt.% incorporated in to an initial Ti0.8Al0.2 powder mixture after 100 h of milling. The hy drogen is found to combine with elemental Ti to form TiH2-x, with an i nitial Ti0.5Al0.5 powder mixture milled for 40 h incorporating 0.95 wt .% H. The milled (TixAl1-x+C) powder mixtures form a large fraction of amorphous phase near x=0.5. Annealing of the as-milled powders incorp orating dissolved carbon and hydrogen produced a mixture of Al2Ti4C2, TiC and TiAl.