Mechanical Alloying Effect on Cu-(Ta,Mo) Powder

Mechanical alloying (MA) of ternary Cu sub 30 Ta sub 70--x Mo sub x (x = 10, 20, 35) was carried out under argon gas atmosphere. The Cu--Ta and Cu--Mo pairs in the ternary Cu--Ta--Mo system are characterized by a positive heat of mixing, while the heat of mixing of the Ta--Mo pair is negative. The X-ray diffraction, DSC, and TEM measurements were used for the study of as-milled and annealed powders. The bcc extended solid solution could be produced by MA of Cu sub 30 Ta sub 35 Mo sub 35 powders. After heat treatment at 600 deg C, the Ta--Mo solid solution formed with exclusion of the whole copper, the fact of which may be attributable to the affinity of Cu--Ta and Cu--Mo pairs. The amorphization of the Cu sub 30 Ta sub 60 Mo sub 10 powders was observed after 200 h of milling, when the content of the tantalum increased. The DSC measurement suggests that the amorphization proceeds through the same process observed in MA of the Cu sub 30 Ta sub 70 powders. In MA, Cu--Be alloys (1.8-2.0 wt.% beryllium) are used.