Transformation and densification of nanocrystalline θ-alumina during sinter forging

C. Scott Nordahl, Gary Lynn Messing

Research output: Contribution to journalArticle

44 Citations (Scopus)

Abstract

The sinter forging behavior of α-Al2O3 seeded and unseeded nanocrystalline (θ-Al2O3 was investigated as a function of temperature, stress, and strain rate. Seeded samples exhibited the highest degree of plastic deformation during the θ- to α-Al2O3 phase transformation. As a result, microstructure control, increased densification, and a higher degree of transformation were obtained. A uniform microstructure of 150 nm α-Al2O3 grains developed, reaching 57% relative density after sintering 1.5 wt% α-Al2O3 seeded samples for 30 min at 1060°C. When sinter forged at 0.25 mm/min to 63 MPa and 1060°C for 30 min large deformations during the phase transformation increased the relative density to 74%. When the stress was increased to 235 MPa (1060°C, 30 min), 99.7% dense α-Al2O3 with a grain size of 230 nm was obtained. By increasing the sinter forging temperature to 1150°C, 99.5% relative density was achieved at 190 MPa for 30 min.

Original languageEnglish (US)
Pages (from-to)3149-3154
Number of pages6
JournalJournal of the American Ceramic Society
Volume79
Issue number12
DOIs
StatePublished - Jan 1 1996

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sinter
Aluminum Oxide
Forging
Densification
aluminum oxide
Alumina
Phase transitions
Microstructure
microstructure
Strain rate
Plastic deformation
Sintering
plastic deformation
strain rate
Temperature
grain size
temperature

All Science Journal Classification (ASJC) codes

  • Ceramics and Composites
  • Materials Chemistry

Cite this

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title = "Transformation and densification of nanocrystalline θ-alumina during sinter forging",
abstract = "The sinter forging behavior of α-Al2O3 seeded and unseeded nanocrystalline (θ-Al2O3 was investigated as a function of temperature, stress, and strain rate. Seeded samples exhibited the highest degree of plastic deformation during the θ- to α-Al2O3 phase transformation. As a result, microstructure control, increased densification, and a higher degree of transformation were obtained. A uniform microstructure of 150 nm α-Al2O3 grains developed, reaching 57{\%} relative density after sintering 1.5 wt{\%} α-Al2O3 seeded samples for 30 min at 1060°C. When sinter forged at 0.25 mm/min to 63 MPa and 1060°C for 30 min large deformations during the phase transformation increased the relative density to 74{\%}. When the stress was increased to 235 MPa (1060°C, 30 min), 99.7{\%} dense α-Al2O3 with a grain size of 230 nm was obtained. By increasing the sinter forging temperature to 1150°C, 99.5{\%} relative density was achieved at 190 MPa for 30 min.",
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Transformation and densification of nanocrystalline θ-alumina during sinter forging. / Nordahl, C. Scott; Messing, Gary Lynn.

In: Journal of the American Ceramic Society, Vol. 79, No. 12, 01.01.1996, p. 3149-3154.

Research output: Contribution to journalArticle

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