PRECIPITATION OF NITROGEN ON DISLOCATION IN NIOBIUM

The kinetics of precipitation of nitrogen in deformed niobium was determined using the Snoek internal friction peak to follow the precipitation. The kinetics followed the well-known rate equation oor the fraction, W, of nitrogen precipitated as a function of time, W = 1 -e-( t τ)n. The constant n was found to be temperature dependent, having the value 2 3 at the lowest temperature used (300°C) and values around 1 at the higher temperatures, 400°C and 500°C. These numbers are correlated with the nature of the precipitates observed in thin film electron microscopy. The predictions of Bullough and Newman concerning the effect on n of discrete and continuous precipitates are well obeyed. © 1969.