Recovery Kinetics of Cold-Deformed Cr-Mo Steels

M. A. VICENTE ALVAREZ; M. MARCHENA; T. PEREZ

METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE

TMS

Año: 2008 vol. 39 p. 3283 - 3290

1073-5623

The recovery kinetics of cold deformed (2.6 and 7 pct) Cr-Mo steel during isothermally and continuous annealing was studied in the 450 °C to 680 °C temperature range. The recovery evolution was monitored by measuring the annealed material yield stress at room temperature, and the microstructure was characterized by the Williamson–Hall X-ray diffraction (XRD) technique. Different responses of the material were observed after long annealing times depending on the amount of prestrain. For low prestrains (2.6 pct), complete recovery was found. For high prestrains (7 pct), partial recovery was observed after long annealing times, with asymptotic yield stress values that depend on the annealing temperature. From XRD measurements, this was ascribed to the formation during annealing of stable structures characterized by low annihilation kinetics with no formation of cells within the grains. This was confirmed by transmission electron observations. To describe the recovery kinetics, a model based on the solution of the differential equation of the dislocation density was used; the process was assumed to be thermally activated, with an activation energy that depends on the dislocation density. The model parameters were fitted with the isothermal annealing results, and an excellent agreement was found when compared to the continuous annealing results.