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Titolo:
Deformation characteristics of polysynthetically twinned (PST) crystals during creep at 1150 K
Autore:
Wegmann, G; Suda, T; Maruyama, K;
Indirizzi:
Tohoku Univ, Dept Mat Sci, Grad Sch Engn, Sendai, Miyagi 9808579, Japan Tohoku Univ Sendai Miyagi Japan 9808579 gn, Sendai, Miyagi 9808579, Japan
Titolo Testata:
INTERMETALLICS
fascicolo: 2, volume: 8, anno: 2000,
pagine: 165 - 177
SICI:
0966-9795(200002)8:2<165:DCOPT(>2.0.ZU;2-N
Fonte:
ISI
Lingua:
ENG
Soggetto:
GAMMA-TITANIUM ALUMINIDES; TIAL ALLOYS; MECHANICAL-PROPERTIES; LAMELLAR STRUCTURE; ROOM-TEMPERATURE; AL; MICROSTRUCTURE; BEHAVIOR;
Keywords:
titanium aluminides, based on TiAl; creep, plastic deformation mechanisms; electron microscopy, transmission;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Engineering, Computing & Technology
Citazioni:
36
Recensione:
Indirizzi per estratti:
Indirizzo: Wegmann, G GKSS Forschungszentrum Inst Werkstofforsch, Max Planck Str, D-21502 Geesthacht, Germany GKSS Forschungszentrum Inst Werkstofforsch Max Planck Str Geesthacht Germany D-21502
Citazione:
G. Wegmann et al., "Deformation characteristics of polysynthetically twinned (PST) crystals during creep at 1150 K", INTERMETALL, 8(2), 2000, pp. 165-177

Abstract

The creep deformation characteristics of a lamellar polysynthetically twinned (PST) crystal of the composition Ti-48 mol% Al was investigated as a function of the lamellar orientation with respect to the compression axis andthe applied stress. The creep resistance of hard PST orientation with the lamellar plates parallel or perpendicular to the compression axis was substantially higher than that of soft orientations with their lamellar plates oriented at intermediate angles to the compression axis. This fact could be associated with the predominant deformation of the hard orientations by deformation modes with the slip plane inclined to the lamellar interfaces in contrast to the predominant deformation of the soft orientations by deformation modes with the slip plane parallel to the lamellar plates. In the soft orientations? mainly straight ordinary dislocations with the Burgers vectorb = 1/2[110] aligned parallel to the lamellar interfaces were encountered in domains with a high resolved shear stress as well as in domains with no reserved shear stress. In the hard orientations? ordinary dislocations b = 1/2[110] and superdislocations with a Burgers vector of the type b = 1/2[112] were observed. Despite a high resolved shear stress in certain oriented domains, superdislocations of the type b = [101] were not found to pray a considerable role during creep deformation under the investigated conditions. Cross twinning contributed to the deformation in favourably oriented variants, but twinning parallel to the lamellar interfaces was much more pronounced in the soft orientations leading to a substantial lamellar refinement. This microstructural hardening during creep results in the observed stressexponents of the soft orientations near unity at high stresses. A change in stress exponent from near unity at high stresses to about 9 at low stresses occurs at about 200 MPa. A critical stress of about 200 MPa for paralleltwinning is proposed as a reason for the change in stress exponent. (C) 2000 Elsevier Science Ltd. All rights reserved.

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Documento generato il 29/09/20 alle ore 00:33:07