Kinetics of static recrystallization in the coarse-grained Fe-40 at.%Al-Zr-B alloy

The aim of works was to describe mathematically the kinetics of static recrystallization of the alloy type Fe-40 at.%Al-Zr-B (with 24.6 Al-0.01 B-0.18 Zr-0.01 C in wt.%) with the coarse-grained structure. The microstructure of the laboratory castings made of this extremely brittle alloy was homogenized by hot rolling of the material in the protective capsules and by the long-term annealing at 1200 degrees C. An initial microstructure with average grain size 0.77 +/- 0.27 mm was obtained. Based on the isothermal plastic deformation tests and EBSD analysis, the static recrystallization kinetics of the prepared coarse-grained B2 iron aluminide after strain 0.20 was mathematically described. Recrystallized fraction depends on deformation/annealing temperature (900-1100 degrees C) as well as on annealing time. The activation energy of static recrystallization was calculated as 255 kJ mol(-1). Competition between dynamic recovery and static recrystallization was proved after strain 0.35 and annealing temperature 1100 degrees C. Static recrystallization starts relatively easily in the studied alloy, but a very long-term annealing is quite necessary for the complete course of recrystallization. The mean size of recrystallized grains falls with the decreasing annealing temperature (0.47 +/- 0.15 mm for temperature 1100 degrees C, and 0.22 +/- 0.04 mm for 900 degrees C). Even at a temperature of 1200 degrees C the annealing after deformation should last approx. 1 min for obtaining the fully recrystallized microstructure. That is why the standard hot forming technologies should be combined by an interpass annealing in order to refine sufficiently the coarse grains. (C) 2017 Politechnika Wroclawska. Published by Elsevier Sp. z o.o. All rights reserved.