Influence of the temperature on the plastic deformation in TiAl |
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Authors: | L Parrini |
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Affiliation: | (1) Present address: Federal Institute of Technology, CH-8082 Zurich, Switzerland;(2) ESEC SA, 6330 Cham, Switzerland |
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Abstract: | A new alloy, Ti-48.6Al-1.9Cr-1.9Nb-1B, with a near-equiaxed γ microstructure and with a lamellar microstructure is investigated by compression tests between 20 and 800 °C and transmission
electron microscopy (TEM). The yield stress exhibits no anomaly as a function of the temperature, while an anomaly, related
to strain hardening, is found at 400 °C in the hardening rate and the activation volume for both the lamellar and nonlamellar
structure. Above 700 °C, a change in the deformation mechanism occurs and the material becomes remarkably softer. The TEM
micrographs highlight the importance of ordinary dislocation motion for both structures at all temperatures. The comparison
with previously reported TEM observations on single-phase TiAl alloys shows definitely that the density of ordinary dislocations
is higher in the investigated two-phase TiAl alloy deformed at room temperature. Also, the presence of the lamellar interfaces
drastically changes the mechanical properties of the alloy and the deformation mechanism. In contrast to the nonlamellar samples,
superdislocations are rare, and twinning is very frequent in the lamellar structure. |
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