On the Evolution of the Amorphous Phase in Cu-Ti Alloys Produced by Mechanical Alloying

Our investigations on the influence of gaseous impurities on the amorphization of CuTi alloys have been extended by X-ray and neutron diffraction measurements on two Cu40Ti60 alloys Mechanically Alloyed (MA) for different periods of time. A Cu40Ti60 alloy made with titanium powder supplied by VENTRON, which has a small (less than 15 percent) impurity of hydrogen, was examined after 2, 4, and 25 h of MA. It showed a regular transition towards the amorphous state. A Cu40Ti60 alloy made with titanium supplied by ALFA (which was free from hydrogen) was examined after 2, 4, 16, 32 and 42 h of MA. It showed a more complex behavior, with the growth of intermetallic phases after only 4 h of MA and an eventual transition to an amorphous alloy with a contamination of a disordered Ti(O,N) mixed oxide/nitride phase. A muon spin resonance spectroscopy experiment was performed on a Cu50Ti50 (VENTRON) sample MA treated for 12 h to look for diffusion of hydrogen. The data from this experiment show that hydrogen begins to diffuse in the temperature interval 160-260 K and that the activation energy obtained is comparable with values for similar structurally disordered hydrides. (Author)