Influence of the temperature on the plastic deformation in TiAl

Abstract

A new alloy, Ti-48.6Al-1.9Cr-1.9Nb-1B, with a near-equiaxed ␥ microstructure and with a lamellar microstructure is investigated by compression tests between 20 and 800 ЊC 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 ЊC in the hardening rate and the activation volume for both the lamellar and nonlamellar structure. Above 700 ЊC, 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.

Influence of chemistry and microstructure on the activation volume of TiAl alloys

“…This yield stress anomaly, which is linked with the character of dislocation cores and slip within geTiAl [29,7], depends on the alloy composition and the presence of impurities [7e9, 11,12,15,16], including in particular the oxygen content (near 1000 ppm in the present alloys, and hence not negligible) [12,16]. It can also be accompanied by plastic instability, as manifest in the presence of strain-ageing effects in geTiAl alloys [52e54].…”

Titanium Aluminide Coating: Structural and Elastic Properties by DFT Approach

“…Experimental works highlighted that the deformation mechanism (α 2 + γ) binary phase is mainly made by ordinary dislocation, super-dislocations, and twinning following the compact plane (111) [4][5][6]. However, TiAl intermetallic compounds suffer from low ductility and toughness at room temperature, which seriously limits their broad range of applications [7].…”