Structure and Thermal Stability of Vacuum Cu-Mo Condensates

The structure of Cu-Mo vacuum condensates was studied by transmission electron microscopy and X-ray diffraction. The components of this system do not form chemical compounds under equilibrium conditions and are mutually insoluble in liquid and solid states. The experimental results indicate that molybdenum atoms are located at the grain boundaries of the copper matrix, predominantly in the form of a monoatomic adsorption layer in the initial condensed state. It has been established that the grain size of the Cu-0.3% Mo condensate is limited by the blocking effect of grain-boundary segregation of molybdenum atoms both during the deposition of the vapor mixture and subsequent annealing. Molybdenum particles formed at the grain boundaries of the copper matrix can have both equilibrium BCC and nonequilibrium FCC crystal lattices. The structure of Cu-0.3% Mo condensates is stable during annealing up to 600 ℃. At temperatures above this, degradation of grain boundary segregations, which initiates the formation of BCC Mo particles and the growth of the copper matrix grains, occurs. Kinetic estimates within the Langmuir monolayer adsorption mechanism and the Zinner mechanism of grain boundary pinning correlate well with the experimental results obtained.