Oxidation mechanisms in bulk Ti2AlC: Influence of the grain size. Issue 5 (May 2020)

• Record Type: Journal Article
• Authors: Yu, Wenbo; Vallet, Maxime; Levraut, Bertrand; Gauthier-Brunet, Véronique; Dubois, Sylvain
• Is Part Of: Journal of the European Ceramic Society. Volume 40:Issue 5(2020)
• Page Start: 1820
• Page End: 1828
• Publication Date: 2020-05
• Subjects: Ti2AlC -- MAX phases -- Oxidation mechanism -- Grain size; Ceramic materials -- Periodicals; Composite materials -- Periodicals; Matériaux céramiques -- Périodiques; Composites -- Périodiques; Ceramic materials; Composite materials; Periodicals; Electronic journals; 666.05
• DOI: 10.1016/j.jeurceramsoc.2020.01.042
• Languages: English
• ISSNs: 0955-2219

Abstract

Abstract: In this work, oxidation mechanisms were studied in fine-grained (FG) and coarse-grained (CG) Ti2 AlC bulk samples. Results showed that the oxidation kinetics are controlled by the grain size of Ti2 AlC. Bigger are the grains, faster is the oxidation. A dense and protective Al2 O3 layer forms at the surface of FG-Ti2 AlC samples while for the CG-Ti2 AlC samples, a thick TiO2 layer forms on top of a discontinuous Al2 O3 . CG-Ti2 AlC was observed to simultaneously transform into Ti3 AlC2 and TiC instead of being directly transformed into TiC. This transformation result in the following crystallographically sandwich-like structure: (0001) Ti2 AlC // (0001) Ti3 AlC2 // (111) TiC. The volume shrinkage associated to this transformation produces elongated holes that are partially filled by α-Al2 O3 . The stress caused by the volume shrinkage generates cracks at the surface, which makes the oxygen inwards diffusion easier and thus worsens the oxidation resistance the CG-Ti2 AlC bulk.