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Titolo:
Oxidation of orthorhombic titanium aluminide Tl-22AL-25NB in air between 650 and 1000 degrees C
Autore:
Leyens, C;
Indirizzi:
DLR, German Aerosp Ctr, Mat Res Inst, D-51170 Cologne, Germany DLR Cologne Germany D-51170 Ctr, Mat Res Inst, D-51170 Cologne, Germany
Titolo Testata:
JOURNAL OF MATERIALS ENGINEERING AND PERFORMANCE
fascicolo: 2, volume: 10, anno: 2001,
pagine: 225 - 230
SICI:
1059-9495(200104)10:2<225:OOOTAT>2.0.ZU;2-0
Fonte:
ISI
Lingua:
ENG
Soggetto:
BEHAVIOR; ALLOYS; RESISTANCE; OXYGEN;
Keywords:
Nh effect; nitride; orthorhombic phase; oxidation oxygen embrittlement; titanium aluminide;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Engineering, Computing & Technology
Citazioni:
23
Recensione:
Indirizzi per estratti:
Indirizzo: Leyens, C DLR, German Aerosp Ctr, Mat Res Inst, D-51170 Cologne, Germany DLR Cologne Germany D-51170 Res Inst, D-51170 Cologne, Germany
Citazione:
C. Leyens, "Oxidation of orthorhombic titanium aluminide Tl-22AL-25NB in air between 650 and 1000 degrees C", J MAT ENG P, 10(2), 2001, pp. 225-230

Abstract

The oxidation behavior of orthorhombic titanium aluminide alloy Ti-22Al-25Nb was studied in air between 650 and 1000 degreesC by isothermal thermogravimetry and postoxidation scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and x-ray diffraction, Microhardness measurements were performed after exposure to gage hardening due to nitrogen and oxygen ingress, The parabolic rate constant of Ti22Al-25Nb was of the same order as conventional titanium alloys and Ti,Al-based titanium aluminides at and below 750 degreesC. Between 800 and 1000 degreesC, the oxidation resistance of Ti-22Al-25Nb was as good as that of gamma -TiAl based aluminides; however the growth rate changed from parabolic to linear after several tens of hours at 900 and 1000 degreesC. The mixed oxide scale consisted of TiO2, AlNbO4, and Al2O3, with TiO2 being the dominant oxide phase, Underneath the oxide scale, a nitride-containing layer formed in the temperature range investigated, and at 1000 degreesC, internal oxidation was observed below this layer. In all cases, oxygen diffused deeply into the subsurface zone and caused severe embrittlement, Microhardness measurements revealed that Ti-22Al-25Nb was hardened in a zone as far as 300 mum below the oxide scale when exposed to air at 900 degreesC for 500 h, The peak hardness depended on exposure time and reached five times the average hardness of the bulk material under the above conditions.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 21/09/20 alle ore 12:34:55