Carbon diffusivity by means of Snoek relaxation in ternary Fe-26 at%(Al+Ga) alloys with different Al/Ga ratio

Abstract

Anelastic relaxation in the temperature range from 0 to 300°C (0.1–30 Hz) in ternary Fe-26(Al+Ga)-0.1Tb alloys is experimentally studied and analysed with respect to binary Fe3Al and Fe3Ga intermetallic compounds. The Snoek-type relaxation due to cyclic stress-induced carbon atom jumps between octahedral interstices in the α-Fe based solid solution (Fe-C-Al,Ga) is recorded and analysed. The Snoek-type effect in the ternary Fe-26(Al+Ga)-0.1Tb alloys has a higher activation energy (up to ∼1.2 eV) in comparison to α-Fe-C (0.83 eV). The relaxation effect demonstrated significant broadening with respect to Debye peak with a single relaxation time and splitting into two separated peaks at a certain ratio Al/Ga. Snoek-type effect provides a unique opportunity to measure C atom diffusivity at relatively low temperatures. Influence of the chemical composition and the measuring frequency on the activation parameters in Fe-26(Al+Ga)-0.1Tb alloys are reported and analysed to estimate the impact of Al and Ga atoms on C atom diffusivity in α-Fe based solid solution.