Effect of titanium on the kinetics of the σ-phase formation in a coarse-grained Fe-Cr alloy

The influence of titanium on the kinetics of the a-phase formation promoted by an isothermal annealing at T = 973 K was studied in coarse-grained quasi-equiatomic Fe-Cr alloys by using the Fe-57 Mossbauer Spectroscopy. It was found that the kinetics could be well-described in terms of the Johnson-Avrami-Mehl equation. The addition of titanium (up to 3 at%) was revealed to effect the transformation kinetics in the following way: for x(Ti) less than or equal to 1.5 at%, its presence accelerates the process with the highest transformation rate for x(Ti) = 0.3 at%, for x(Ti) greater than or equal to 1.5 at%, titanium retards the formation of the sigma-phase. Quantitatively, the effect of titanium on the kinetics was described in terms of a change of the effective activation energy. (C) 2000 Elsevier Science Ltd. All rights reserved.