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MÖSSBAUER STUDIES OF SOLUTE ATOM ASSOCIATED WITH LATTICE DEFECTS IN
METALS
Y. Ishida, T. Ozawa, H. Ichinose, K. Sassa, M. Taniwaki, S. Umeyama, S.
Ogawa
To cite this version:
Y. Ishida, T. Ozawa, H. Ichinose, K. Sassa, M. Taniwaki, et al.. MÖSSBAUER STUDIES OF SO-
LUTE ATOM ASSOCIATED WITH LATTICE DEFECTS IN METALS. Journal de Physique Col-
loques, 1979, 40 (C2), pp.C2-571-C2-572. �10.1051/jphyscol:19792199�. �jpa-00218577�
MQSSBAUER STUDIES OF SOLUTE ATOM ASSOCIATED WITH LATTICE DEFECTS IN METALS
Y. Ishida, T. Ozawa, H. Ichinose, K. Sassa, M. Taniwaki, S. Umeyama and S. Ogawa Institute of Industrial Science, University of Tokyo, 7 Roppongi, Minato, Tokyo, Japan
Abstract.- Recent Mossbauer experiments of the laboratory on the lattice defects are tabulated. Two specific works; (1) defect structures in Al-5 Co alloys introduced by electron irradiation and (2) grain boundary embrittlement by the segregation of ''9mSn in binary iron alloys are described.
1. Introduction.- Recent developments of high reso- lution electron microscopy stimulate the Mossbauer study of the lattice defects, since the interpreta- tion of Mossbauer spectrum can be made more specific when the atomic configuration at the defect is known.
The electronic, lattice dynamical or diffusion re- lated parameters are useful means to understand the role of the defects on the engineering properties of metals /l/ 111.
In this paper the authors intend to show some general aspects of the recent Mossbauer defect re- searches of the laboratory /3/-/7/ and also introdu- ce some individual works of the laboratory. The pre- sent report together with six papers of the labora- tory contained in this proceedings update our for- mer one 181 presented at Bendor Conference in 1974.
2. Mossbauer experiments of the lattice defect in the laboratory.- Table I lists researches recently carried out in the laboratory. Research works marked by * are included in this proceedings. Those with
+ mark are contained in this paper. The researches may be devided into two areas; studies of point
defects and of the grain boundary. The former is carried out mainly with aluminium and aluminium alloys, since the association of impurity elements with the lattice defects is the major controlling
features of the aging behavior. The study of grain boundary segregation, on the other hand, was concer- ned with iron and iron alloys because the segrega- tion of IVb to VIb elements (including tin) to the grain boundary is the major cause of the embrittle- ment. The grain boundary study is extended to two directions; the alloy study and the analysis of bi- crystal boundary. The latter will give unique infor- mation of the boundary properties as a function of
the grain boundary structures.
3. Characteristic problems associated with the de- fect experiments.- There are two major problems li- miting the lattice defect experiments;
(1) Smallness of the defect concentration (2) Multiplicity of defect structures.
The present authors have approached the first problem via two routes; specimen preparation and Mossbauer source experiment. The former approach
Table I : Mossbauer researches of the laboratory A. Interactions with point and the secondary defects
quenched Al-57Fe alloy Ichinose et al /3/-/47 quenched Al-57Co alloy* Sassa et al lb I
57Fe ion-implanted to Al* Sassa et al electron irradiation to Al-57Co alloy*
quenched Al- 1 9Sn alloy* Umeyama et al.
quenched Al-Cu-Sn, Al-Zn-Sn alloys* Taniwaki et al /6/
B. Grain boundary segregation
fine grain pure iron* Ozawa & Ishida 111 Fe-Mn, Ti, Cr and Ni alloys'1"
Q O O ] twist boundaries of Ag* Ichinose et al Works marked by * are reported in this proceedings.
JOURNAL DE PHYSIQUE Colloque C2, supplément au n° 3, Tome 40, mars 1979, page C2-571
Résumé.- Les études récentes du laboratoire dans le domaine des défauts de réseau caractérisés par spectrométrie Mossbauer sont recensées. On décrit plus particulièrement deux travaux : (1) les dé- fauts de structure dans des alliages Al-57Co irradiés aux électrons et (2) la fragilisation aux joints de grain par ségrégation de '1 , mS n dans des alliages binaires du fer.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19792199
c2-572 JOURNAL DE PHYSIQUE
consisted of various thermal or physical treatments the evil elements.
of the specimen to increase the defect concentration.
The secondary effect due to the specimen treatments as well as that of the high defect concentration it- self is inherent to the technique.M%sbauer source experiments are free fromthe problem. The detection limit of " g m ~ n and 5 7 ~ o in aluminium and iron alloys was lo-', the concentration is exceeded easily by
that of the lattice defects. The absorption due to S 7 ~ e atoms associated with the vacancies was only a sub-peak with the A1-2 x
lo-'
5 7 ~ e alloy 131 141, while with the A1-5 xlo-'
5 7 ~ o alloy /5/ the spec- trum became the major one and allowed the quantita- tive analysis.The multiplicity of the species is inherent with the defect structures which are metastable. Sys-
tematic investigation on simple systems such as querr ched, irradiated or ion-implanted pure aluminium is indispensable before analyzing engineering systems.
With the grain boundary study one major problem was multiplicity of grain boundaries contributing to the Mgssbauer spectrum. The effect of grain boundary structure to the lattice dynamical property is in- vestigated for thin foil bicrystals of silver.
4. Study of lattice defects introduced by electron irradiation in A~-'~co alloys.- Researches of the irradiation-induced lattice defects are important to develop nuclear fusion reactor wall material and semiconductor devices. Vbgl et a1 191-/lo/ recently performed irradiation experiments at liquid helium temperature with AL-~'CO alloys using both neutron and electron. They observed that the interstitial 5 7 ~ o formed at 41K and annihilated at 260K when va- cancies migrated to the 5 7 ~ o . The spectrum corres- ponding to 5 7 ~ o associated with vacancies was not observed. The authors performed electron irradiation experiments at liquid nitrogen temperature with the same A~-'~co alloys to observe the vacancy peak. The Mgssbauer spectrum changes during isochronal aging of the specimen showed that the peak corresponding to the interstitial "CO of V6g1 et a1 was overwhel- ming. An increase in the recoilless fraction during annealing, however, suggested superimposition of a small vacancy peak.
5. The binding state of tin segregated at the grain boundary of binary iron alloys.- Grain boundary embrittlement of low alloyed steels by the segrega- tion of IVb to VIb elements is strongly influenced by third elements. Manganese, Chromium and nickel are known to enhance the phenomenon, while titanium pre- vents the embrittlement in spite of the presence of
There is a theory which attributes the embrittle- ment to the donation of electrons from the segregated elements to d shell of iron at the grain boundary /Ill. If the loss of coherency at the grain boundary is due to the electronic effect, titanium with more empty d shell is likely to absorb the electrons and preserve the bonding force of iron at the boundary.
The information may be obtained from the isomer shifts of l L g m ~ n segregated at the boundary of binary iron alloys containing the above "third" elemnts.
The table I1 lists some preliminary results.
Table I1 : Msssbauer parameters of l l g m ~ n segregated in the grain boundary of iron alloys.
A1 loy G(mm/s) hD(K) H (KOe )
- -
pure Fe 1.64 295 0
Fe- 1 %Ti 1.60 284 0
Fe- I %Cr 1.69 24 6 0
Fe-3%Mn 1.64 27 1 0
Fe- I %Ni 1.84 338 12
The isomer shifts of the table I1 indicate that electrons of " g m ~ n contribute to bonding most strongly with the Fe-Ti alloy, which seems to support the theory that titanium atoms are really taking electrons to their very empty d shells.
The authorsacknowledge Pr. Emeritus M. Kato for nucleating the research project, Dr. H. Yoshida at Research Reactor Institute, Kyoto University for cooperating with the electron irradiation experiments, and International Atomic Energy Agency for a finan- cial support of the research program.
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