Structure, stacking faults and electrochemical behavior of α-Ta prepared by chemical vapor deposition

Using X-ray diffraction, scanning electron microscopy, glow discharge emission spectroscopy, electrochemistry and strength assessment, stacking faults in tantalum deposited in a helium environment on a copper substrate by chemical vapor deposition and their effect on the protective properties have been studied. It is shown that the probability of formation of stacking faults in deposited bcc tantalum in the {112} planes is a sensitive parameter with respect to the deposition conditions (temperature and helium content). With an increase in helium concentration from high to medium values, the sum of the probabilities of the formation of deformation (α) and twinning (β) stacking faults 1.5α + β in α-Ta increases five times (from 0.025 to 0.13%), with a decrease in temperature from 800 to 750°C — 35 times (from 0.025 to 0.89%). A decrease in the probability of formation of stacking defects in deposited α-Ta tantalum is associated with a significant increase in corrosion resistance and adhesion strength of the coating to the substrate. A mechanism for the formation of metastable hcp phases of tantalum on stacking faults in α-Ta in the {112} planes is proposed.