Micromechanical Origins and Design Implications of Damage Tolerance in Ti3SiC2
Final rept. 2000-2003
DREXEL UNIV PHILADELPHIA PA DEPT OF MATERIALS ENGINEERING
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The goals of the proposed work were to elucidate the microstructural and atomic origins of the mechanical properties exhibited by Ti3 SiC2 The focus is on the micro-mechanisms of inelastic deformation and their contribution to the damage tolerance exhibited by this compound. In addition to being technologically important, a basic study of the structure-property relations in this compound will be beneficial to understanding the behavior of the entire class of layered ternary carbides and nitrides. There are over 60 of these identified to date, During this work we conducted and successfully completed an extensive investigation of the mechanical response at two different length scales macro simple compression tests and micro scale nano-indentations. Additionally, we also completed extensive investigations on graphite. Our measurements revealed several unique features that are common to both of these layered materials, in comparison to other conventional ceramics. Our studies have revealed that the reversible, rate-independent, hysteretic stress-strain curves exhibited is attributable to incipient kink banding, which at higher stress levels or temperatures leads to irreversible deformation caused by formation of kink bands. Remarkably, the hysteretic energy dissipated in each cycle in the MAX phases can be as high as 25 of the elastic stored energy.
- Military Aircraft Operations
- Metallurgy and Metallography