On the origin of acoustic emission during room temperature compressive deformation of a γ-TiAl based alloy

An energy approach to the formation of twins in TiAl

“…The activity of mechanical twinning was investigated in a two-phase alloy with a neargamma microstructure by acoustic emission. [9,10] Accordingly, the contribution of mechanical twinning is significant at the beginning of deformation, and then it decreases. At larger strains, deformation is mainly provided by dislocation glide, a behavior that was confirmed by micromechanical modeling.…”

“…At larger strains, deformation is mainly provided by dislocation glide, a behavior that was confirmed by micromechanical modeling. [9,10] Thus, in terms of the von Mises criterion for a general plastic shape change of polycrystalline material, there is a lack of independent slip systems that can be activated at given stress. In grains or lamellae that are unfavorably oriented for glide of ordinary dislocations or twinning, significant constraint stresses can be developed due to the shape change of deformed adjacent grains.…”

“…The length of the twins is essentially limited by the widths of the ␥ grains or lamellae, and the typical thickness is in the range of 15 to 20 nm [5,9,10] (Figure 1). According to the authors' knowledge, there is no model available that satisfactorily accounts for these structural features.…”

Microstructure and Properties of Engineering Materials

“…Figure 1.8a shows the presence of dislocations and mechanical twins in a deformed γ-TiAl grain within a Ti-46.5 at.%Al-4 at.%(Cr, Nb, Ta, B) alloy. From the TEM image it is evident that in the observed γ-grain more than one twin system has been activated [30,31]. Analytical TEM measurements such as EDX and electron energy-loss spectroscopy (EELS) allow to determine the chemical composition of individual phases, particles, or at interfaces.…”

A Dislocation-Scale Characterization of the Evolution of Deformation Microstructures around Nanoindentation Imprints in a TiAl alloy

“…Despite intense research on the HT behavior of TiAl alloys, literature suffers from a lack of 26 understanding on their RT behavior particularly on the elementary deformation mechanisms and the 27 precise role of microstructures [6] [7] [8].…”