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 σ-phase formation promoted by an isothermal annealing at T=973 K was studied in coarse-grained quasi-equiatomic Fe–Cr alloys by using the 57Fe Mössbauer 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 xTi⩽1.5 at%, its presence accelerates the process with the highest transformation rate for xTi=0.3 at%, for xTi⩾1.5 at%, titanium retards the formation of the σ-phase. Quantitatively, the effect of titanium on the kinetics was described in terms of a change of the effective activation energy.