Orientation Dependence of Pseudoelasticity in Fe_3Al Single Crystals

摘要

FeaAl single crystals grown by a floating zone method were compressed at different orientations to examine the orientation dependence of the pseudoelasticity. DO_3-ordered Fe-23.0at%Al single crystals with an appropriate heat treatment demonstrated a giant pseudoelasticity, although martensitic transformation never occurs in the crystals. In the crystals, a superpartial dislocation with Burgers vector of 1/4<111> moved individually dragging antiphase boundary (APB). A restoring force due to the APB resulted in a giant pseudoelasticity. The strain recovery during unloading depended strongly on crystal orientation. The single crystals oriented for planar slip on (101) plane showed a large strain recovery as much as 5.0%. In contrast, the strain recovery at crystal orientation for easy cross slip or multiple slip was smaller than that for planar slip on (101 ) plane. The forest dislocations or dislocation debris formed by the interaction between several slips hindered the reversible motion of superpartials with b=l/4<111> in both the anti-twinning and the twinning senses. Moreover, the amount of strain recovery in the twinning sense was larger than that in the anti-twinning sense, suggesting that the pseudoelasticity in Fe_3Al crystals was influenced by the asymmetry of core structure of the superpartials with a screw character.