Mechanical Properties of the TaSi2 Fibers by Nanoindentation

The Si-TaSi2 eutectic in situ composite, which has highly-aligned and uniformly-distributed TaSi2 fibers in the Si matrix, can be obtained when the solidification rate changes from 0.3 to 9.0 mm/min. It is very interesting that one or two TaSi2 fibers are curved when the solidification rate reaches 6.0 mm/min, although it is very brittle in general. The formation mechanism of the curved fiber is discussed and mechanical properties of the TaSi2 fibers are examined by nanoindentation. It is found that the hardness and the elastic modulus of the bended TaSi2 fiber are much higher than that of the straight TaSi2 fiber. Moreover, the reasons why the mechanical properties of the straight TaSi2 fiber are different from that of the curved TaSi2 fiber are discussed. This can be ascribed to internal stress which results from mismatch of the thermal expansion coefficients of the two phases and di erent crystallographic orientations.