Anelasticity in Fe-Al-Cr alloys at elevated temperatures

Several (Fe,Cr)(3)Al alloys with Cr content from 3 to 25% have been studied in the temperature range from 680 to 930 K using isothermal frequency dependent tests (from 10(-4) to 10(2) Hz). Three relaxation peaks were observed in this range. The Zener relaxation (P1 peak) caused by reorientation of pairs of substitute atoms in Fe is observed in all studied alloys and used to evaluate the activation parameters of substitute atom jumps in Fe. Activation parameters of the Zener peak in Fe-26Al-Cr depend not too much on Cr content (H = 275-290 kJ/mol, tau(0) = 10(-19) to 10(-20) s), while the relaxation strength increases with the increase in Al + Cr content. The second internal friction peak (P2) at higher temperatures with similar activation energies but higher tau(0) (10(-17) to 10(-19) s) is observed only in Cr containing alloys but not in Fe-25Al binary alloy. Most probably this peak is controlled by dislocations motion in Fe-26Al-Cr alloys. The third peak, denoted as P3 (H = 428 kJ/mol, tau(0) = 10(-25) s), was observed only in the Fe-25Al-25Cr alloy and was classified as a grain boundary peak. (C) 2009 Published by Elsevier B.V.