Experimental Micromechanics Study of Lamellar TiA1
Final technical rept. 15 Apr 2003-14 Apr 2006
STATE UNIV OF NEW YORK AT STONY BROOK DEPT OF MECHANICAL ENGINEERING
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A unique micro-scale full field deformation measurement technique called electron speckle photography is exploited to investigate the deformation mechanism of lamellar TiAl. We find the size of the specimen used and the area of strain measurement affect the mechanical properties thus obtained. The strain distribution inside a grain is highly heterogeneous. The grain boundary is much stiffer than the interior of the grain. We also observe several interesting phenomena of the material when a crack is present. Crack speed tends to slow down when the crack approaches a grain boundary. Within a grain the slowest propagation speed is when the lamellar layers are perpendicular to the crack. Crack may jump across a grain boundary and its propagation direction may be predicted by the strain concentration congregated near the grain boundary. By mapping the deformation field surrounding the crack tip, we can evaluate the mode mixity from the speckle results at different stages of crack propagation.
- Inorganic Chemistry