Aging of Iron-Based Martensites at Low Temperatures

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dc.contributor Aalto-yliopisto fi
dc.contributor Aalto University en Ullakko, Kari 2015-05-25T09:00:46Z 2015-05-25T09:00:46Z 1992
dc.identifier.isbn 978-951-22-9934-8 (electronic)
dc.identifier.isbn 951-22-1101-7 (printed)
dc.description.abstract In the present work aging of iron-based martensites, defined as all the phenomena preceding the first stage of tempering, is studied using various methods. In some alloys aging was observed to start at very low temperatures, even near 4 K. Abnormally high or abnormally low tetragonality is observed in freshly formed martensite alloyed with Ni or Mn, respectively. The reason for high tetragonality obviously lies in the coherency at the interface between the martensite and the retained austenite. It is shown in the present work that the coherency is broken during aging in the temperature range of 100 - 200 K and it is accompanied by a decrease of tetragonality (first stage of aging). The new internal friction peak centered at 145 K corresponds to the movement of the coherent interface and the break of coherency. Some evidence for correlation between short range atomic ordering in austenite and the high tetragonality of the virgin martensite is given and a contribution of nontransformed ordered austenitic regions inside martensite plates to tetragonality is discussed. It is shown that the second stage of aging at temperatures about 200 - 270 K is controlled by the pinning of the dislocations by carbon atoms and the third stage (mainly above 250 K) by the clustering of carbon atoms in a solid solution. By means of Mössbauer spectroscopy, electrical resistivity and magnetic susceptibility measurements, a striking difference is shown between the redistribution of carbon and nitrogen atoms above 200 K. Evidence for the clustering of carbon and ordering of nitrogen is given and discussed. The dynamics of clustering was studied by means of small angle neutron scattering. Deformation of martensite at subambient temperatures reduced the tetragonality of martensite to cubic and changed the redistribution of carbon atoms. According to different measurements, practically no aging was observed below room temperature in the deformed martensite. en
dc.format.extent 74
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher Helsinki University of Technology en
dc.publisher Teknillinen korkeakoulu fi
dc.relation.haspart [Publication 1]: K. Ullakko and V.G. Gavriljuk, Effects of coherent interfaces in the freshly formed iron–nickel–carbon martensites, Acta Metallurgica et Materialia, Overview No. 99, Vol. 40, No. 10, pp. 2471-2482, 1992. DOI:10.1016/0956-7151(92)90316-7
dc.relation.haspart [Publication 2]: O. Antson, V.G. Gavrilyuk, V.A. Kudryashov, V.M. Nadutov, H. Pöyry, J. Pietikäinen, A. Tiitta, V.A. Trudnov, K. Ullakko, V.A. Ul'yanov, P. Hiismäki and Yu.P. Chernenkov, Neutron diffraction study of the martensitic transformation in Fe–Ni–C alloys, Physics of Metals and Metallography, Vol. 70, No. 4, pp. 108-115, 1990.
dc.relation.haspart [Publication 3]: V.G. Gavrilyuk, V.M. Nadutov, S.P. Oshkaderov, J. Pietikäinen and K. Ullakko, Phase and magnetic transformations in the Fe–Ni–C alloy at low temperatures, Physics of Metals and Metallography, Vol. 70, No. 1, pp. 120-125, 1990.
dc.relation.haspart [Publication 4]: V. Gavriljuk, V. Duz' and K. Ullakko, Internal friction of tempered ferrous martensites, Scripta Metallurgica et Materialia, Vol. 26, pp. 667-672, 1992. DOI:10.1016/0956-716X(92)90303-V
dc.relation.haspart [Publication 5]: V.G. Gavriljuk, V.M. Nadutov and K. Ullakko, Low temperature ageing of Fe-N martensite, Scripta Metallurgica et Materialia, Vol. 25, pp. 905-910, 1991. DOI: 10.1016/0956-716X(91)90246-W
dc.relation.haspart [Publication 6]: V.V. Runov, A.I. Okorokov, A.D. Tretjakov, L.V. Grigorjev, V.A. Uljanov, K. Ullakko and V.G. Gavriljuk, Observation of a relaxation phenomenon during ageing of Fe-Ni-C martensite by means of small angle neutron scattering, Scripta Metallurgica et Materialia, Vol. 26, pp. 661-665, 1992. DOI:10.1016/0956-716X(92)90302-U
dc.relation.haspart [Publication 7]: M. Kajatkari, K. Ullakko and J. Pietikäinen, On the aging of Fe-Ni-C and Fe-Mn-C martensites, Journal de Physique, Colloque C4, Supplément au no 18, Tome 43, décembre 1982, pp. 461-466. DOI: 10.1051/jphyscol:1982471
dc.relation.haspart [Publication 8]: K. Ullakko, M. Nieminen and J. Pietikäinen, Effects of low temperature deformation on the lattice structure and carbon distribution in Fe-Ni-C martensite, Materials Science Forum, Vols. 56-58 (1990), pp. 191-196. DOI: 10.4028/
dc.subject.other Physics en
dc.title Aging of Iron-Based Martensites at Low Temperatures en
dc.type G5 Artikkeliväitöskirja fi Insinööritieteiden korkeakoulu fi School of Engineering en
dc.contributor.department Laboratory of Engineering Materials en
dc.subject.keyword martensite en
dc.subject.keyword aging en
dc.subject.keyword low temperature en
dc.subject.keyword deformation en
dc.subject.keyword X-ray diffraction en
dc.subject.keyword neutron scattering en
dc.subject.keyword Mössbauer spectroscopy en
dc.subject.keyword internal friction en
dc.subject.keyword positron annihilation en
dc.subject.keyword electrical resistivity en
dc.subject.keyword magnetic susceptibility en
dc.subject.keyword dilatometry en
dc.subject.keyword shear modulus en
dc.identifier.urn URN:ISBN:978-951-22-9934-8
dc.type.dcmitype text en
dc.type.ontasot Doctoral dissertation (article-based) en
dc.type.ontasot Väitöskirja (artikkeli) fi
dc.contributor.supervisor Pietikäinen, Juha
dc.contributor.supervisor Hänninen, Hannu 1992-06-25

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