Abstract
In order to investigate the dynamic mechanical behavior of TiAl alloys and promote their application in the aerospace industry, uniaxial compression of Ti-44Al-4Nb-1.5Mo-0.007Y (at %) alloy was conducted at a temperature range from 25 to 400 °C with a strain rate of 2000 s‒1. Twinning is found to be the dominating deformation mechanism of the γ phase at all temperatures, and the addition of Nb and Mo has a chemical impact on the alloy and reduces the stacking fault energy of the γ phase. The decreased stacking fault energy increases the twinnability; thus, the deformation is dominated by twinning, which increases the dynamic strength of the alloy. With the temperature increasing from 25 to 400 °C, the average spacing of twins in the γ phase increases from 32.4 ± 2.9 to 88.1 ± 9.2 nm. The increased temperature impedes the continuous movement of partial dislocations and finally results in an increased twin spacing in the γ phase.
Highlights
Titanium aluminum (TiAl) alloys are considered to be one of the most promising candidates for high temperature applications in the aerospace industry because of their high strength, low density and excellent creep properties [1,2,3]
Conventional TiAl alloys, consisting of the γ phase and α2 phase, have drawbacks such as low ductility at room temperature and poor hot workability [6,7]
The present paper aims at investigating the mechanical properties and deformation mechanisms of TNM alloys at temperatures of 25 ◦ C, 200 ◦ C and 400 ◦ C with a high strain rate using a split Hopkinson pressure bar (SHPB)
Summary
Titanium aluminum (TiAl) alloys are considered to be one of the most promising candidates for high temperature applications in the aerospace industry because of their high strength, low density and excellent creep properties [1,2,3]. Conventional TiAl alloys (for example, Ti-48Al-2Cr-2Nb alloy), consisting of the γ phase and α2 phase, have drawbacks such as low ductility (elongation is less than 5%) at room temperature and poor hot workability [6,7]. These disadvantages of TiAl alloys can be improved significantly by thermo-mechanical processing, such as hot rolling, hot forging, and hot extrusion [8], which reduces the number of voids and refines grain sizes. In order to improve the mechanical properties as well as the hot workability of TiAl alloys, TNM alloys ( called β phase containing TiAl alloys) have been developed in recent years. In addition to the γ and α2 phases, a disordered β phase exists in TNM alloys at a temperature range from 1100 to 1300 ◦ C, which is mainly stabilized by Nb and other minor elements such as Mo, Cr, Y, etc. [13], and effectively improves the hot workability and plasticity
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