Abstract
The dynamic recrystallization (DRX) behavior of Ti-45Al-8.5Nb-0.2W-0.2B-0.3Y (at %) alloy has been investigated through hot compression tests. The tests were executed at a temperature range of 1000–1200 °C and a strain rate range of 0.001–1 s−1 under a true strain of 0.9. It was found that the α2 phase which is produced during heat treatment is reduced during hot compression due to thermo-mechanical coupling. The value of the activation energy is 506.38 KJ/mol. With the increase in deformation temperature and the decrease in strain rate, DRX is more likely to occur, as a result of sufficient time and energy for the DRX process. Furthermore, the volume fraction of high angle grain boundaries increases to 89.01% at a temperature of 1200 °C and the strain rate of 0.001 s−1, meaning completely dynamic recrystallization. In addition, DRX is related to the formation of twin boundaries. The volume fraction of twin boundaries rises to 16.93% at the same condition of completely dynamic recrystallization.
Highlights
TiAl-based alloys are considered a promising candidate for high-temperature structural applications in the aerospace and automotive industries [1,2,3,4] because of their outstanding properties such as low density, high specific yield strength, high specific stiffness, good oxidation resistance and creep properties
It has been found that the addition of Nb can improve the workability of ductile β/B2 phase at elevated temperatures [7,8], and Nb and W tend to enrich in β/B2 phase, which contributes to the stability of β/B2 phase [9]
Microstructure evolution is affected by hot deformation parameters, especially by deformation temperature, strain rate and degree of deformation [15,16]
Summary
TiAl-based alloys are considered a promising candidate for high-temperature structural applications in the aerospace and automotive industries [1,2,3,4] because of their outstanding properties such as low density, high specific yield strength, high specific stiffness, good oxidation resistance and creep properties. In order to improve the hot workability of TiAl-based alloys, many studies have been performed over the last two decades [5,6]. It is commonly agreed that service properties are significantly connected with microstructures. It is well-known that hot deformation is an effective method to optimize the microstructure, to further improve these properties. Microstructure evolution is affected by hot deformation parameters, especially by deformation temperature, strain rate and degree of deformation [15,16]
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