Tensile properties and internal friction of thermally aged (773K) Fe–1wt%Cu alloys were measured as a function of Cu precipitation between 100 and 600K. Two regimes were clearly identified in terms of yield stress at low temperatures below 250K. It was found that in the over-aged samples the yield stress decreased much more abruptly with the temperature than in the specimens annealed at shorter time. The internal friction spectra showed the existence of similar features in all samples, which indicated that no drastic change of the microstructure occurred during aging. These results suggest that the lack of softening at low temperatures originates principally from thermally-activated kink-pair formation and gliding processes, controlled by the size and/or density of Cu-precipitates.

Tensile Properties and Internal Friction Study of Dislocation Movement in Iron–Copper System as a Function of Copper Precipitation. M.J.Konstantinović, A.Almazouzi, M.Scibetta, E.van Walle: Journal of Nuclear Materials, 2007, 362[2-3], 283-6