In situ observation of pseudoelasticity in Fe3Al single crystals with D03 structure

Abstract

In order to clarify the mechanism of pseudoelasticity in Fe23.0Al (at%) single crystals with the D03 structure, in situ observation of tensile deformation was performed at room temperature using an optical microscope (OM), an electron back-scatter diffraction (EBSD) device and an X-ray Laue back-reflection (XLBR) machine. In the present study, neither martensite nor twin was observed during the pseudoelasticity. In particular, the whole of the tensile specimen could be indexed with respect to the D03 structure by in situ EBSD measurement. (1̄1̄2), (1̄01) and (2̄11) slips were confirmed to occur depending on the loading axis by in situ OM observation. When (1̄01) [111] slip was activated, coarse slip bands parallel to (1̄01) slip plane were formed during loading. The area fraction of the slip bands increased linearly with increasing plastic strain up to 0.066. During unloading, the slip bands disappeared, resulting in pseudoelasticity. From in situ XLBR tests, the crystal rotation of the loading axis toward [111] slip direction took place during loading. The rotation angle and the plastic strain satisfied the Schmid-Boas relationship at small plastic strains, especially for (1̄1̄2) and (2̄11) slips. These results suggest that the reversible motion of 1/4〈111〉 superpartial dislocation dragging an antiphase boundary (APB) was responsible for the pseudoelasticity in Fe-23.0Al single crystals. © 2014 The Japan Institute of Metals and Materials.