Pseudoelasticity in Fe3Ga single crystals
Introduction
Pseudoelasticity generally results from a thermoelastic martensitic transformation: a stress-assisted transformation during loading and the reverse transformation during unloading [1]. In contrast, Fe3Al single crystals with the D03 structure exhibited pseudoelasticity though martensitic transformation never occurred in these crystals [2], [3], [4]. The amount of shape recovery in Fe3Al single crystals showed a maximum at around 23.0at.%Al and the recoverable strain was approximately 5.0% [3], comparable with that of Ti–Ni alloys [1]. In Fe-rich Fe3Al single crystals with Al contents between 22.0 at.% and 25.0 at.%, superpartial dislocations with Burgers vector (b) of 1/4〈1 1 1〉 moved individually dragging the nearest-neighbour antiphase boundary (NNAPB) during loading, though four superpartials bound by NNAPB and next-nearest-neighbour antiphase boundaries (NNNAPB) moved in a group in Al-rich Fe3Al [3]. In Fe-rich Fe3Al, NNAPB pulled back the superpartials during unloading, resulting in the pseudoelasticity. We call this phenomenon “APB pseudoelasticity”.
Both aluminium and gallium are IIIB-group elements. Furthermore, Fe3Ga is known to have the D03 structure in the temperature range 873–923 K [5]. Thus, there is a possibility that Fe3Ga single crystals as well as Fe3Al demonstrate APB pseudoelasticity irrespective of the martensitic transformation. However, pseudoelasticity has not yet been reported for Fe–Ga alloys. In the present study, we discovered for the first time pseudoelasticity in Fe3Ga single crystals. It is strongly suggested that APB pseudoelasticity appeared in these single crystals, similar to Fe3Al.
Section snippets
Experimental procedure
A master ingot of Fe3Ga was prepared in a plasma arc furnace. A Fe3Ga single crystal was grown from the ingot by the floating zone method at a growth rate of 5 mm/h. The chemical composition of the crystal was determined to be Fe–24.2at.%Ga by a wet chemical analysis. After homogenisation at 1373 K for 48 h, the single crystal rod was solution treated at 1073 K for 1 h and subsequently quenched in ice brine. After quenching, the samples were annealed at 853–923 K for ordering. According to a Fe–Ga
Results and discussion
Fig. 1 shows a stress–strain curve of Fe–24.2at.%Ga single crystal annealed at 873 K for 10 h and then compressed to εp = 5.0%. A stress–strain curve of Fe–23.0at.%Al single crystal [3] is also shown in the figure. Fe3Ga single crystal yields at 561 MPa and shows weak work hardening during loading, while a plastic strain of 5.0% is completely recovered during unloading. Moreover, the shape of the stress–strain curve of Fe–24.2at.%Ga single crystal is quite similar to that of Fe–23.0at.%Al crystal
Conclusions
Fe–24.2at.%Ga single crystal with an appropriate heat treatment exhibited pseudoelasticity, though a thermoelastic martensitic transformation never occurred in the crystals. NNAPB and NNNAPB may pull back the superpartials with b = 1/4[1 1 1] during unloading in the crystal, resulting in the pseudoelasticity.
Acknowledgments
This work was supported by a Grant-in Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan. Part of this work was carried out at the Strategic Research Base “Handai Frontier Research Centre” supported by the Japanese Government’s Special Coordination Fund for Promoting Science and Technology. This work was also supported by “Priority Assistance of the Formation of Worldwide Renowned Centers of Research—The 21st Century COE Program
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Cited by (21)
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2014, Computational Materials ScienceCitation Excerpt :The purpose of this paper is to propose a mesoscale model incorporating back stresses responsible for cyclic reversible dislocation motion. It has been reported that single crystals of Fe3Ga with the cubic D03 structure exhibit pseudoelasticity of several percent strain and these recoverable strains are comparable to NiTi alloys [21]. The reversible slip in Fe3Ga and Fe3Al can occur over a broader range of temperature [21–24].
Anomalous growth of antiphase domains in Ti<inf>3</inf>Al
2009, Scripta MaterialiaMultimode pseudoelasticity in Fe-23.8 at% Ga single crystals with D0<inf>3</inf> structure
2008, IntermetallicsCitation Excerpt :Fe3Ga is a Fe-based intermetallic compound with the D03 superstructure of which single-phase field exists around 873–923 K [4]. We first observed that Fe3Ga single crystals with the D03 structure demonstrated giant pseudoelasticity irrespective of martensitic transformation [5,6]. In the D03 structure (Fig. 1(a)), a 〈111〉 superdislocation is generally dissociated into four 1/4〈111〉 superpartials bound by the nearest-neighbour (NN) and next-nearest-neighbour (NNN) antiphase boundaries (APB) as shown in Fig. 1(b) [7].
Effect of heat treatment on pseudoelasticity in Fe-25.0 at.% Al single crystals
2006, IntermetallicsCitation Excerpt :% was favourable for the appearance of perfect pseudoelasticity. More recently, we also found that D03-ordered Fe3Ga single crystals showed giant pseudoelasticity arising from the to-and-fro motion of 1/4〈111〉 superpartials [11]. According to the Fe–Al phase diagram shown in Fig. 1, the transformation pathway of Fe–25.0 at.