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Crack Healing in Ti2Al0.5Sn0.5C-Al2O3 Composites.

Authors :: Bei, Guo Ping
Pedimonte, Birgit Joana
Pezoldt, Marc
Ast, Johannes
Fey, Tobias
Goeken, Mathias
Greil, Peter
Wakai, F.
Source :: Journal of the American Ceramic Society; May2015, Vol. 98 Issue 5, p1604-1610, 7p, 1 Color Photograph, 1 Black and White Photograph, 2 Charts, 3 Graphs
Publication Year :: 2015
Abstract: Oxidation induced crack healing of Al<subscript>2</subscript>O<subscript>3</subscript> composites loaded with a MAX phase based repair filler (Ti<subscript>2</subscript>Al<subscript>0.5</subscript>Sn<subscript>0.5</subscript>C) was examined. The fracture strength of 20 vol% repair filler loaded composites containing artificial indent cracks recovered fully to the level of the virgin material upon isothermal annealing in air atmosphere after 48 h at 700°C and 0.5 h at 900°C. SEM- EBSD analysis of crack microstructure indicates two different oxidation reaction regimes to govern the crack filling: near the surface SnO<subscript>2</subscript>, TiO<subscript>2</subscript>, and Al<subscript>2</subscript>O<subscript>3</subscript> were formed whereas deeply inside the cracks Al<subscript>2</subscript>O<subscript>3</subscript> and TiO<subscript>2</subscript> and metallic Sn were detected. The presence of elemental Sn was attributed to partial oxidation of aluminum and titanium which lowered the local oxygen concentration below a threshold value required for Sn oxidation to SnO<subscript>2</subscript>. Thus, Ti<subscript>2</subscript>Al<subscript>0.5</subscript>Sn<subscript>0.5</subscript>C may represent an efficient repair filler system to trigger oxidation induced crack healing in ceramic composites at temperatures below 1000°C. [ABSTRACT FROM AUTHOR]