Internal friction studies of carbon and its redistribution kinetics in Inconel 600 and 690 alloys under dynamic strain aging conditions

Carbon Snoek-like relaxation peak with a height of about 10−4 was found in annealed nickel-based Inconel 600 alloy at 620–670 K while no carbon-induced peaks were observed in Inconel 690 alloy. The activation enthalpy and the pre-exponential factor of the relaxation time are 1.68 ± 0.09 eV and 10−14.14±0.72 s, respectively. The height of the observed peak increases dramatically, up to about 10−3, after tensile deformation of the Inconel 600 alloy at 423 K at the strain rate of 10−5 s−1, when dynamic strain aging (DSA) behavior exhibits well developed serrations on the tensile stress–strain curve. Annealing in situ at the carbon peak temperature results in decay of the peak amplitude, which consists of two exponential stages with characteristic times of 1.6 and 21.9 ks, respectively. The first characteristic time is in good agreement with the mean period of DSA serrations. The second characteristic time probably presents the re-growth of carbides partly dissolved during prior deformation in DSA conditions.