Effect of strain-rate on the deformation response of D03-ordered Fe3Al

The mechanical response of centrifugally cast Fe(3)A1 with the composition Fe-27A1 (at.%) containing microalloying additions of Nb, Zr, C, and B was investigated over a wide range of strain rates between 10(-4) and 10(3) s(-1) at room temperature. Tests were carried out in compression using a (i) screw-driven load frame, (ii) drop impact tester, and (iii) split-Hopkinson pressure bar at quasi-static, intermediate and dynamic strain rates respectively. Post deformation analysis was carried out by DSC, SEM/EBSD, TEM and micropillar deformation. In all instances, the stress-strain curves show initial hardening (-first 5% plastic strain) followed by a plateau in stress. A loss in work-hardening occurs at the highest strain rates examined (>10(3) s(-1)) and is likely associated with shear localization; in addition, (2 11) [11 1]-type twinning was observed at these high strain rates at room temperature. This observation is in line with previous theoretical calculations of the antiphase boundary (APB) energy. The consequence of a continuously increasing yield stress with strain rate and a loss in work hardening at the highest strain rates together yields a maximum in flow stress at the intermediate strain rate. (c) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.