Alumina–Aluminide Alloys (3A) Technology: II, Modeling of Ti_xAl_y–Al₂O₃ Composites Formation

Abstract

The reaction sintering of Ti x Al y -Al 2 O 3 composites from TiO 2 /Al starting powder mixtures has been characterized by thermogravimetry and differential thermal analysis (TG/ DTA), in situ temperature measurements, and predictions via a continuum model. In order to model the TiO 2 /Al reaction system, it was necessary to first determine the postmill reactant concentrations and the dominant reaction. The postmill reactant concentrations were obtained from TG/DTA measurements in air, while X-ray diffraction (XRD) was used to gain insight into the reaction mechanisms. A continuum model of the process was fitted to in situ temperature measurements by adjusting two parameters. The model was then used to investigate the effects of various processing conditions on the reaction behavior.

Sliding wear of Cr–Al2O3–ZrO2 and Mo–Al2O3–ZrO2 composites

“…TiO 2 or Fe 2 O 3 , is converted to a composite consisting of aluminides and alumina by a redox reaction between aluminum and the metal oxide. [2][3][4][5][6][7] Because these redox reactions are usually highly exothermic, careful process control is required in order to avoid thermal runaway with possible detrimental effects on the product. In contrast to this, s-MAC precursors consist of Al 2 O 3 , a metal powder such as Cr, Mo, or Fe, and only a small fraction, typically <1 wt.%, of Al.…”

Solid-state reactions during heating mechanically milled Al/TiO2 composite powders

“…[5][6][7][8][9][10] This process makes use of the fact that the reduction of such oxides by Al results in formation of another metal and aluminum oxide (typically Al 2 O 3 ). [2][3][4][5][6][7][8][9][10] The work was mainly focused on producing Al alloy-based MMCs and Al 3 Ti-based IMCs. On the other hand, the aluminum oxide, especially ␣-Al 2 O 3 , is a good ceramic reinforcement material for MMC or IMC.…”

“…The metal can be a good matrix material by itself, or a good alloying element for Al matrix, or form intermetallic phases with Al, which can also work as a matrix material. [5,10] High-energy mechanical milling is a very effective process for producing composite powders. The use of the reaction between Al and TiO 2 in producing in-situ MMCs and IMCs is particularly attractive, since Al-Ti or Ti-Al alloys or titanium aluminides are favorable matrix materials.…”

Characterization of α-Al2O3–(Al–Si)3Ti composites

“…10,11 The intermediate phases that were observed as a result of the different heat treatments include: titanium oxides (TiO, Ti 2 O 3 ), Al-Ti intermetallics (TiAl, Ti 3 Al) and ␥-Al 2 O 3 . 10,11 This work probes the unique microstructure and various reactions that take place during the different stages of production of partially reinforced lightweight structural components, based on Al 2 O 3 -TiO 2 preforms that were infiltrated by commercial Al-alloys.…”

“…8,9 The i-3A process is based on pressure infiltration of liquid Alalloys into a porous preform, which is composed of Al 2 O 3 and a reactive oxide (such as TiO 2 , Nb 2 O 5 or Fe 2 O 3 ). In TiO 2 based CMC, a reduction reaction takes place, where Al 3 Ti is produced by the reduction of TiO 2 by Al according to: 10,11 3TiO 2 + 13Al → · · · → 3Al 3 Ti + 2α-Al 2 O 3 (1)…”