実験報告書様式（一般利用課題・成果公開利用）（ ※本報告書は英語で記述してください。ただし、産業利用課題として採択されている方は日本語で記述していただいても結構です。 ）MLF	 Experimental Report

提出日 Date of Report

課題番号 Project No.

装置責任者 Name of responsible person

2014A0094

Kazya AIZAWA and Stefanus HARJO

実験課題名 Title of experiment

装置名 Name of Instrument/（BL No.）

In-situ Neutron Diffraction Study on Tensile-Compression

TAKUMI (BL 19)

Deformation Behavior of 18R-LPSO Mg alloy

実施日 Date of Experiment

実験責任者名 Name of principal investigator

May/18/2014-May/21/2014

Satoshi MOROOKA所属 Affiliation

Tokyo Metropolitan 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.

The nominal composition of the Mg–Zn–RE alloy used in the present study is Mg85Zn6Y9 (at.%). Masteralloy ingot was prepared either by high frequency induction melting of pure metals in an argon atmosphereor by furnace melting of pure metals in a steel tube under a CO2 atmosphere, followed by casting into awater-cooled copper mold. The obtained microstructure is almost 18R-Long Period Stacking Order (LPSO)
phase structure and a few casting defect.

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.

【Experimental method】 The in-situ TOF neutron diffraction during tension-compression cyclic loading
was performed at room temperature by using TAKUMI (BL19). The bar type testing specimens for in-situ
experiments with a gauge length of 6 mm, diameter of Φ5 mm were machined from the Mg casting alloy.
TAKUMI is equipped with tension-compression tester mounted on the diffractometer, with its loading axis
turned 45 degrees with respect to the incident beam. There are two detector banks, which measuretime-resolved diffraction patterns at fixed horizontal scattering angles of ±90 degrees. The two detectorbanks thus measure diffraction patterns from grains oriented in axial and transverse geometry with respect
to the applied stress. The sampling volume for neutron diffraction is wide range at the parallel position ofthe tensile specimen, so that bulky averaged information is obtained. An event mode of data acquisition
system employed at MLF enable us to analyze the obtained data by changing data slicing time interval aftertesting. Taking statistic sufficiency into consideration, the time interval can be decreased with increasing of
neutron beam intensity.
12. 実験方法及び結果（つづき） Experimental method and results (continued)

At room temperature, cyclic testing was performed using high-precision extensometer under fully-reversed
cyclic loading conditions at constant maximum and minimum strain amplitudes of +0.5 % and -0.5 %. The
cyclic strain increasing rate was 2×10-4 %/sec. The initial loading was tensile. Cyclic data were collected at
N= 1, 2, 3, 4, 5, 10, 30, 50, 75, 100, 150, 175 cycles. During the tension-compression cycles above, four
points along the hysteresis loop were studied, as shown in Fig. 1. These points coincide with the maximum
tensile (Pts 1 and 5) and the maximum compressive strain (Pt 3), the two zero-stress points (Pts 2 and 4).
The applied stress at the maximum tension (Pt 5) and the maximum compression (Pt 3) as a function of
number of cycles (Fig. 2) demonstrate almost the hardening region of tension-compression cycles. The
failure-life time of this alloy was 218 cycles.

Fig. 1 The stress-strain curves of the initial tensile loading and the four measurement points within the firsttension-compression cycle. Pts 2 and 4 are at 0 MPa; Pt 3 is at -0.5 %; Pts 1 and 5 are at +0.5 % strain,respectively.

Fig. 2 The stress evolution at the maximum tension (Pt 5) and compression (Pt 3) as a function of numberof cycles.
【Experimental result】
The tension-compression regime with strain amplitude control is considered in this work. Fig.1 illustrates
a stress-strain loop under strain-controlled cycling. During initial loading, yielding is observed in the stress2

2. 実験方法及び結果（つづき） Experimental method and results (continued)

strain curve before the 1st-tension-compression cycle (Fig. 1).On unloading, plastic strain is seen at 0 MPa(Pt 2). The compression to a -0.5 % strain (Pt 3) shows a nonlinear stress-strain response. In reloading intension through 0 MPa (Pt 4) and +0.5 % strain (Pt5), the hysteresis loop develops. Fig. 2 shows an increaseof peak stresses in both tension and compression with increasing number of cycles resulting in cyclic
hardening up to the 200th cycle. At the 200th tension-compression cycle, tension and compression peakstresses are approximately +97.4 and –176.7 MPa, respectively. The both peak stresses are different.
Because, it suggests that kinking (quasi-twinning) was occurred by compression deformation.
The flow curves of tension-compression continuous loading are presented in Fig. 3 for Mg85Zn6Y9 castingalloy with fully 18R-LPSO phase structure. During the initial tensile loading, all of the internal latticestrains evolve linearly, indicating that all grains are elastic up to a stress 30 MPa, at which point thediffraction peaks diverge from linearity. The nonlinearity in the internal strain development occurs at asignificantly lower stress than the 0.2% proof stress identified by the applied stress-strain curve andsignifies microyielding; the initiation of plasticity within some of the grains. Post yield, family grains with a{60.0} plane normal parallel to the loading direction start accommodating a greater portion of the strain
elastically while family grains with a {00.18} plane normal parallel to the loading direction startaccommodating less elastic strain. This indicates that the latter are yielding as they now accommodate someof their deformation by plastic strain rather than elastic strain and that the former must, thus carry more of
the applied load.
Therefore, the hysteresis loop of 18R-LPSO phase structure {60.0} strain is much different from that of{00.18}, showing that the intergranular stress built up during the forward deformation accelerates thebackward plastic flow resulting in an increase of the Bauschinger stress and Bauschinger strain.

Fig. 3 Results of tension-compression test for Mg85Zn6Y9 casting alloy: (a) changes in {00.18} and {60.0}
lattice strains during the test shown in (b) and (b) Applied stress-strain curve (beam power: 300 kW).

3