Microstructure characterization in superplastically deformed silicon nitride

Journal Article · Tue Apr 01 04:00:00 EST 1997 · Journal of the American Ceramic Society

DOI:https://doi.org/10.1111/j.1151-2916.1997.tb02917.x· OSTI ID:509232

Burger, P; Duclos, R; Crampon, J ^[1]

---

1. Univ. des Sciences et Technologies de Lille, Velleneuve-d`Ascq. (France). Lab. de Structure et Proprietes de l`Etat Solide

Fully dense silicon nitride (Si{sub 3}N{sub 4}) has been produced by hot isostatically pressing {alpha}-Si{sub 3}N{sub 4} powder at 1,740 C under 160 MPa, with 0.5 wt % Y{sub 2}O{sub 3} and 0.5 wt % Al{sub 2}O{sub 3} as sintering additives. The sintered material was composed of very fine (0.5 {micro}m) and equiaxed grains, as required for superplasticity. Before deformation, a very small amount of intergranular glassy silicate-based film was detected by transmission electron microscopy at the two-grain and triple-point junctions. Compression tests with a strain value of up to {approximately}0.5 were conducted in nitrogen in the temperature range of 1,600--1,700 C. The observation of a shear-thickening phenomenon and the presence of a transition from a mild to a strong strain hardening at 20 MPa were attributed to the occurrence of rigid contacts between the grains. The angular distribution of the observed strain whorls was used to evidence the increase of rigid contacts between the grains, under the local expulsion of the wetting liquid film, with increases in compressive stress.

• Sponsoring Organization: USDOE
• OSTI ID: 509232
• Journal Information: Journal of the American Ceramic Society, Journal Name: Journal of the American Ceramic Society Journal Issue: 4 Vol. 80; ISSN 0002-7820; ISSN JACTAW
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM OXIDES
DEFORMATION
GRAIN BOUNDARIES
HOT PRESSING
MICROSTRUCTURE
NITROGEN
SILICON NITRIDES
STRAIN HARDENING
STRAINS
TEMPERATURE RANGE 1000-4000 K
YTTRIUM OXIDES