Slip transfer across γ-TiAl lamellae in tension

Publication date: 15 May 2018
Source:Materials & Design, Volume 146
Author(s): Alberto Jesús Palomares-García, María Teresa Pérez-Prado, Jon Mikel Molina-Aldareguia
This work identifies the mechanisms governing dislocation transmission across lamellar interfaces in a Ti-45Al-2Nb-2Mn (at.%) + 0.8(vol%) TiB2 (Ti4522XD) alloy. With this aim, a microgrip and a microtensile specimen were designed and fabricated using a focused ion beam (FIB), to test micrometer-sized specimens in tension. The deformation mechanisms acting in a microtensile specimen of a Ti4522XD alloy were investigated through electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The results revealed that domain boundaries (order variant) and lamellar interfaces (order variant, true twin and pseudo-twin) are relatively transparent to dislocation propagation, but they present significant differences in the geometrical alignment between the incoming and outgoing slip systems. While for order variant interfaces, the incoming and outgoing slip systems are perfectly aligned, true twin and pseudo twin interfaces require a change in slip plane and direction, which leaves residual dislocations with Burgers vectors lying on the interface plane. The analysis of the slip transfer mechanisms revealed that the outgoing slip system is governed more by the maximum geometrical alignment, than the applied resolved shear stress.

Graphical abstract

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