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
課題番号 Project No. 2016A0024

提出日 Date of Report
装置責任者 Name of responsible person
Yasuhiro Miyake

実験課題名 Title of experiment

装置名 Name of Instrument/（BL No.）

Vacancy and hydrogen behavior in Al-Mg-Zn alloys

D1

実験責任者名 Name of principal investigator

実施日 Date of ExperimentKatsuhiko Nishimura

January 17 – January 19 (2 days)

所属 Affiliation
University of Toyama
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.
1. Al - 3.4 at.% Zn - 1.9 at.% Mg heat treated at 753 K for 1000 minutes and quenched into ice-water on January
14 (four days before the measurement). (noted as Al-Zn-Mg AQ-4d)
2. Al - 3.4 at.% Zn - 1.9 at.% Mg heat treated at 423 K for 400 minutes. (Al-Zn-Mg 150C)
3. Al of a purity 99.99% (base Al); which was used to make Al-Zn-Mg alloys.
4. hydrogen charged Al of a purity 99.99 % by the plasma charging method (Al-H)*5. Al - 3.4 at.% Zn - 1.9 at.% Mg heat treated at 753 K for 1 hour and quenched into ice-water (1 hour before
measurement). (Al-Zn-Mg AQ)*6. Al of a purity 99.99% heat treated at 848 K for 1 hour and quenched into ice-water. (base Al AQ)

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.

All the samples were mounted on the spectrometer at D1 beam line.

After evacuating the sample space, wemeasured the temperature dependence of zero-field spin relaxation spectra increasing temperature from 10 K,then 20K to 300 K with a step of 20 K, accumulating 15 mega events at each temperature.
field of 20 G was measured for a period of 3 mega vents at 10 K.

TF spectrum with a

Due to the limited beam intensity, thus arelatively low counting rate, we decided to acquire basic data sets of zero-field spin relaxation for Al-Zn-Mg
alloy with the samples of Al-Zn-Mg AQ-4d, Al-Zn-Mg 150C, base Al and Al-H.
four samples were completed.

The measurements with these

However, the last two samples, Al-Zn-Mg AQ and base Al AQ, which would

show non-equilibrium state of vacancy, were not explored this time.
The observed zero-field muon spin relaxation spectra were shown in the Figs. 1 for Al-Zn-Mg alloys and 2 forbase Al and hydrogen charged base Al. In Fig. 1, it is obvious that muon were trapped in certain sites of bothAl-Zn-Mg samples at 20 K since the spectra showed a typical shape of the Kubo-Toyabe function.
elevated temperature of 140 K, however, there is a clear difference on the relaxation spectra.
Al-Zn-Mg AQ-4d sample relaxed faster than those in the Al-Zn-Mg 150C.
1

At theMuon spins in theThe density of the trapping sites of2. 実験方法及び結果（つづき） Experimental method and results (continued)
Al-Zn-Mg is considered to be much higher than the number of muon
particles, so the difference of the relaxation rate at this temperature ispossibly due to the difference of micro structures of Zn/Mg/vacancy
clusters.
A pure aluminum is known to be quite transparent to positive muons.
It is also known that a muon trapping rate is quite sensitive to impurities
and defects.

The present base aluminum, which was used to make

Al-Zn-Mg alloys, has a purity of 99.99 %, which means there existing
about 100 ppm impurities.

Fig. 1

Fig. 2 shows muon spin relaxations in thebase Al sample at 200 K due to the impurities and defects.

This kind ofrelaxation behavior, however, almost disappeared at 280 K.

Thehydrogen charged aluminum sample, Al-H, indicates the faster spin
relaxations than those of the base aluminum, thus there are some effects on
the spin relaxation originated in the charged hydrogen.
The data analysis has been done following the similar procedure in ourprevious studies.

All the observed spectra were compared with relaxation

functions built by a Monte Carlo simulation, in which four variable

Fig. 2parameters were employed: the dipolar width (Δ), trapping rate (t),detrapping rate (d), and fraction of initially trapped muons (p0) [S.
Wenner et al.; Phys. Rev. B86, 104201 (2012)]. An ensemble of 60
million muons are simulated to produce a five dimensional relaxation
function f (Δ, t, d, p0, time) [E. Sato, et al.; Hyper. Inter. 17-19, 203-210(1984)].

Fig. 3 shows examples of the data analysis of the trapping

rates deduced from the spectra obtained with Al-Zn-Mg samples. The
temperature dependences of the trapping rates of the two samples aredifferent between 40 and 120 K. We made an attempt to estimate an

Fig. 3trapping potential energy of Zn/Mg/vacancy clusters, assuming relations:ddtdexp(-Q/kT) (Q: trapping potential energy). A least-square
fit of the data yielded the Q value of 5.2 (+-0.6) meV for Al-Zn-Mg 150C, and4.6 (+-0.2) meV for Al-Zn-Mg AQ-4d. These values are a bit larger thanthat of 3.6 (+-0.4) meV obtained in Al-Mg-Si alloys [K. Nishimura et al.; J
Phys. Conf. Ser. 551, 012031(2014) ].
Fig. 4 shows the extracted values of the dipole widths for the base andhydrogen charged aluminum samples.

There is no significant differences

at low and medium temperatures, but there is a clear difference above 220K.

Fig. 4At this temperature region, muons are mostly trapped by deep potential sites produced by vacancies.

This

result implies, therefore, that the charged hydrogens also trapped near vacancies, which increased dipole fields
acting on the muons.
2