Structural modifications during heating of bulk nanocrystalline FeAl produced by high-pressure torsion

The deformation-induced nanostructure developed during high-pressure torsion of B2 long-range ordered FeAl is shown to be unstable upon heating. The structural changes were analyzed using transmission electron microscopy, differential scanning calorimetry and microhardness measurements. Heating up to 220 degrees C leads to the recurrence of the chemical long-range order that is destroyed during deformation. It is shown that the transition to the long-range-ordered phase evolves in the form of small ordered domains homogeneously distributed inside the nanosized grains. At temperatures between 220 and 370 degrees C recovery of dislocations and antiphase boundary faults cause a reduction in the grain size from 77 to 35 nm. Grain growth occurs at temperatures above 370 degrees C. The evolution of the strength monitored by microhardness is discussed in the framework of grain-size hardening and hardening by defect recovery. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.