Annealing-induced recrystallization of iron after high pressure torsion at 80 K

Abstract

Grain growth during recrystallization of pure iron with a submicrocrystalline structure formed by 5 revolutions of an anvil of high-pressure torsion deformation at cryogenic temperature (80 К) has been studied by transmission and scanning electron microscopy and durometry. Annealing at 523 К has significantly developed recrystallization (to 90 % of the material volume). The average recrystallized grain size is 2 μm. The primary recrystallization has been completed after 1‑h annealing at 823 К, forming grains with an average grain size of 6.5 μm. Annealing at 823 К has resulted in a large number of fine grains due to the formation of thermally activated centers of recrystallization. The grain size variability, which is characterized by the formation of grains with a size of five or more times greater than the average grain size, is observed. The average grain size has remained unchanged according to the scanning electron microscopy data, and decreased according to transmission electron microscopy data. The recrystallization texture of an axial <110> type has formed during annealing at 823 К. An increase in the annealing temperature to 923 К has increased the sharpness of the recrystallization texture. The hardness of iron has remained dependent on the true strain (distance from the sample center) after annealing at all temperatures under study.