A shear-type allotropie transformation in alumina

Wynnyckyj, J. R.; Morris, Christopher G.

doi:10.1007/bf02679726

Cited by 37 publications

(18 citation statements)

References 15 publications

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“…The δ-to θ-alumina transformation is also believed to be a diffusive process, but the details of the structural rearrangement on the atomic level are not well understood (27,28). It has been proposed that the θ-to α-alumina transformation occurs via either a "synchoshear" (martensitic) process, requiring a critical grain size of the θ-alumina prior to transformation (27), or a nucleation and growth type process (28).…”

Section: Effects Of Aging On Aluminamentioning

confidence: 99%

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Microstructural Evolution of γ-Alumina-Supported Rh upon Aging in Air

Weng-Sieh

Gronsky

Bell

1997

Journal of Catalysis

125

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Section: Effects Of Aging On Aluminamentioning

confidence: 99%

“…How metal oxide impurities accelerate or inhibit the phase transformation processes is the subject of ongoing research (26)(27)(28).…”

Section: Effects Of Aging On Aluminamentioning

confidence: 99%

Microstructural Evolution of γ-Alumina-Supported Rh upon Aging in Air

Weng-Sieh

Gronsky

Bell

1997

Journal of Catalysis

125

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“…These phenomena imply that the presence of Fe accelerates the translormation 0-to alpha-A1203 because of the transient formation of hexagonal cL-Fe20:,, which favors the nucleation of o~-A1203 [23]. As suggested by Burtin et al [241 and confirmed recently by Pint et al [16], it is believed tlhat larger foreign ions such as Y, Zr, l~a, Hf, and Th residing in a relatively open, cubic 0-AIzO~ lattice inhibit the diffusionless martensitic-type transformation to a hexagonal ~x-A1203 lattice by requiring more energy to overcome the distortion [24,25], whereas smaller foreign ions such as Ti, Mg and Ga accelerate the transformation to a [24]. Although the effect of Fe ions on the O-to ~-A1203 transformation in /3-NiAI has not been previously discussed, the Fe ions having a similar ionic size as Ti appear to have acted as an accelerator.…”

Section: Resultsmentioning

confidence: 77%

The effect of fe on high temperature oxidation of NiAl

Jeong

Lee

1998

Metals and Materials

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A study was conducted to observe the (~xidation of NiAl+3.5at.%Fe alloy in ~-NiAI phase field at air temperatures of 1000, 1200 and 1400"C, and these results were compared with those of pure NiAI alloys. The primary effects of the Fe-addition in NiAI were round to be: l) decrease in oxidation resistance and adherence of scales during both isothermal and cyclic oxidation tests, 2) enhancement of phase transformation rate from 0-to a-AI20,, 3) more rapid fl)rmation of characteristically ridged a-Al~O~ scales during initial ,:)xidation stages, and 4) partial scaling of voids formed at the scale-substrate interlace and dissolulion of Fe inside the alumina scale by the ~mtward diffusion of Fe from the substrate alh~y.

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“…10b, which indicating that Ti 2 O 3 may also have formed. From these results, it is reasonable to conclude that the accelerated transformation to a-Al 2 O 3 was caused by the initial formation of oxides which have corundum remaining about whether the transformation is diffusion controlled or diffusion-less, i.e., a martensitic transformation [20]. [22].…”

Section: Resultsmentioning

confidence: 90%

Acceleration of Metastable to Alpha Transformation of Al2O3 Scale on Fe–Al Alloy by Pure-Metal Coatings at 900 °C

et al. 2010

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The effect of pure-metal coatings on the transformation of a pre-formed h-Al 2 O 3 scale on an Fe-50Al alloy was investigated. The elements Fe, Cr, Ti, and Ni were deposited on the pre-formed Al 2 O 3 having a thickness of about 50 nm. Ti, Cr or Fe coatings on pre-formed h-Al 2 O 3 were found to accelerate the transformation to a-Al 2 O 3 , while no apparent effect was observed from the Ni coating. Since the corundum crystal structure of Ti 2 O 3 , Cr 2 O 3 and Fe 2 O 3 was indentified on Ti, Cr or Fe coated samples and the transformation to a-Al 2 O 3 started at the outer part of the h-Al 2 O 3 scale, these corundum oxides were considered to act as heterogeneous nucleation sites for a-Al 2 O 3 , therefore promoting the transformation from h-Al 2 O 3 to a-Al 2 O 3 . The growth rate of a-Al 2 O 3 grains and the rate of advance of the h-Al 2 O 3 /a-Al 2 O 3 interface were found to be faster with the Fe coating.

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A shear-type allotropie transformation in alumina

Cited by 37 publications

References 15 publications

Microstructural Evolution of γ-Alumina-Supported Rh upon Aging in Air

Microstructural Evolution of γ-Alumina-Supported Rh upon Aging in Air

The effect of fe on high temperature oxidation of NiAl

Acceleration of Metastable to Alpha Transformation of Al2O3 Scale on Fe–Al Alloy by Pure-Metal Coatings at 900 °C

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