実験報告書様式（一般利用課題・成果公開利用）

MLF Experimental Report

提出日 Date of Report
March, 2010

課題番号 Project No.

装置責任者 Name of responsible person

2009B0004

Kazuya Aizawa, Stefanus Harjo

実験課題名 Title of experiment

装置名 Name of Instrument/（BL No.）In situ neutron diffraction study for Fe-based shape memory

BL19materials

実施日 Date of Experiment

実験責任者名 Name of principal investigator

January, 27, 28, 30, 2010

Hiroyuki Y. Yasuda
所属 Affiliation
Osaka University
試料、実験方法、利用の結果得られた主なデータ、考察、結論等を、記述して下さい。（適宜、図表添付のこと）
Please report your samples, experimental method and results, discussion and conclusions. Please add figures andtables for better explanation.
1. 試料 Name of sample(s) and chemical formula, or compositions including physical form.
(A) Fe-Al single crystals and polycrystals
・Fe-23at%Al single crystals with different loading axes
・Fe-23at%Al polycrystals(B) Fe-Ga single crystals and polycrystals
・Fe-24at%Ga single crystals and polycrystals
・Fe-28at%Ga polycrystals(C) Co-50at%Zr polycrystals

2. 実験方法及び結果 （実験がうまくいかなかった場合、その理由を記述してください。）
Experimental method and results.

If you failed to conduct experiment as planned, please describe reasons.

In situ neutron diffraction study was carried out to examine deformation behavior of Fe-Al and Fe-Ga shapememory materials with the D03 superlattice structure. We also studied the deformation behavior of CoZr alloys
which is a potential candidate for hydrogen permeable film.
A. in situ neutron diffraction study for Fe-Al alloys
Fe-23at%Al single crystals were tensile deformed withdifferent orientations at room temperature and in situ neutron
diffraction was taken by engineering diffractometer TAKUMI(BL19). No diffraction peak corresponding to martensitic
transformation could not be detected during loading-unloading
cycle. In contrast, the position and FWHM of the neutron

Fig.1

Superelasticity

based

on

dislocation motion.

diffraction peaks were consistent with superelasticity based on dislocation motion, schematically shown in Fig.
1. Figure 2 shows change in (420) peak of Fe-23at%Al single crystals with nominal strain (ε). The angle between[420] direction and loading axis is 6.4°. At the onset of plastic deformation, the (420) peak shifts to higher lattice12. 実験方法及び結果（つづき） Experimental method and results (continued)
spacings due to tensile elastic strain. At 2% ≤ ε ≤ 5%, peakbroadening occurs corresponding to the accumulation ofdislocations. At the initial stage of unloading, the (420) peakshift to lower plane spacings because of the release of elasticstrain. The (420) peak becomes sharp by further unloading
since the dislocations disappear. After unloading, the positionand FWHM of the (420) peaks is almost the same as those
before loading. In situ neutron diffraction study was also
carried out for Fe-23at%Al polycrystals compressed to 5 % atroom temperature. Even after deformation to 5 %, all thediffraction peaks could be indexed with respect to the D03

Fig.2 Variation in (420) peak with tensile
strain in Fe-23at%Al single crystal pulled atroom temperature.

structure. This also suggests that the superelastic deformationin Fe-23at%Al alloys is not based on martensitic transformation
but dislocation motion shown in Fig. 1.
B. in situ neutron diffraction study for Fe-Ga alloys
Fe-Gaalloys

solutionizedat900℃

exhibitedsuperelasticity partly based on martensitic transformation.
Figure 3 shows neutron diffraction profiles of Fe-24at%Ga
polycrystals compressed to 1 % at room temperature. At ε=1 %,Fig.3 Neutron diffraction profiles ofFe-24at%Ga polycrystals compressed atroom temperature.

a small new peak is observed in the vicinity of (220) peak. We
also observed the new peak in the diffraction profiles inFe-28at%Ga polycrystals subjected to compression. Thus, one
can conclude that reversible martensitic transformation as wellas

dislocation

motionduringloading-unloading

cycle

contributes to the superelasticity in Fe-Ga alloys.
C. in situ neutron diffraction study for CoZr alloys
B2-ordered CoZr grains of which loading axis is [001]cannot be plastically deformed since the slip system of CoZr is{110}<001>. Thus, the [001]-oriented grains behave as a
hard-grain in the polycrystals which may lead to strong

Fig.4 Variation in lattice plane strain withapplied stress in CoZr polycrystals during
tensile loading.

stress/strain partitioning. Figure 4 shows variation in spacing of(200), (220) and (111) planes with applied stress during tensile deformation of CoZr polycrystals. Note that theplanes were almost perpendicular to the tensile axis. As shown in Fig. 4, CoZr polycrystals demonstrate strong
stress/strain partitioning. At the initial stage of tensile deformation, the lattice spacing of (200), (220) and (111)planes increases with increasing applied stress. On the other hand, the spacing of (220) and (111) planes tends tobe saturated above the yield stress (150 MPa). In contrast, the (200) plane spacing rises monotonically even after
the yielding. Thus, strong stress/strain partitioning was confirmed to occur in CoZr alloys by in situ neutron
diffraction study.
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