Key Takeaways & Executive Findings
- •• Adding 0.4 at.% Ta to Ti46Al1.5Cr8Nb alloy yields optimal compressive properties: strength of 2,434 MPa and strain of 33.1%. • Ta addition refines lamellar colony size from 160.65 μm to 94.44 μm and increases B2 phase content from 12.49% to 21.91%. • Ta shifts solidification path to lower Al concentrations, enhancing supercooling and promoting phase refinement. • Property improvement is attributed to lamellar colony refinement, solid solution strengthening, and reduced c/a ratio of γ phase.
Abstract
The microstructure of high Nb-TiAl alloys was optimized by the addition of a small amount of Ta elements to further improve their properties. A series of Ti46Al1.5Cr8Nb-xTa (x=0.2, 0.4, 0.6, 0.8, 1.0, at.%) alloys were prepared by vacuum arc melting. The microstructure, mechanical properties, and related influencing mechanisms were systematically investigated. The results indicate that the solidification microstructure of the Ti46Al1.5Cr8Nb-xTa alloys comprises the γ-TiAl phase, α2-Ti3Al phase, and B2 phase. As the Ta content increases from 0.2at.% to 1.0at.%, the content of α2 phase and B2 phase increases, while the γ phase content decreases. Among them, the B2 phase shows the most pronounced change, being significantly refined, with its content increasing from 12.49% to 21.91%. In addition, the average size of the lamellar colony decreases from 160.65 to 94.44 μm. The addition of the Ta element shifts the solidification path toward lower aluminum concentrations, leading to changes in phase content. The tantalum-induced increase in the B2 phase and enhanced supercooling at the solidification front provide the basis for lamellar colony refinement. Compressive testing at room temperature reveals that the Ti46Al1.5Cr8Nb0.4Ta alloy exhibits optimal compressive properties, achieving a compressive strength of 2,434 MPa and a compressive strain of 33.1%. The improvement of its properties is attributed to a combination of lamellar colony refinement, solid solution strengthening resulting from the incorporation of Ta element, and a reduction in the c/a of the γ phase.
1. Introduction
TiAl alloys are widely regarded as ideal candidates for structural materials in areas such as aerospace and automotive, owing to their low density, high specific strength, and excellent creep resistance. They have been successfully utilized in components like aero-engine blades and automotive exhaust systems [1-3]. However, limitations in high-temperature performance and room-temperature ductility hinder their broader engineering use [4, 5]. To improve the properties of TiAl alloys, many researchers have attempted to do so by adding alloying elements or improving the preparation process [6-8]. For TiAl alloys exhibiting poor hot workability, low-cost and efficient alloying represents a particularly suitable approach.
The incorporation of high-melting-point Nb elements into TiAl alloys can significantly enhance the high-temperature performance of the alloys. Consequently, high-Nb TiAl alloys are regarded as a new generation of TiAl alloys suitable for higher operating temperatures [9, 10]. In recent years, Ta element as an element belonging to the same VA group as Nb element, has gained increasing attention from researchers due to its higher melting point and superior performance compared to Nb element in certain aspects. For example, Lapin et al. [11] compared the microstructures of Ti46Al8Nb and Ti46Al8Ta after directional solidification and found that Ta exhibited better grain-refining effects than Nb in TiAl alloys. Vojtěch et al. [12] found that Ta was more effective than Nb in reducing the oxidation rate of TiAl alloys when comparing the oxidation resistance of Ti-45.2Al-7.2Nb and Ti-44.8Al-6.6Ta alloys. Moreover, Luo et al. [13] found that the addition of an appropriate amount of Ta element can effectively improve the room-temperature plasticity of TiAl alloys. Liu et al. [14] corroborated this finding by preparing Ti48Al2Cr2Nb-xTa alloys using a laser additive manufacturing technique. Their results showed that the addition of 0.5at.% Ta enhanced the room-temperature strength and elongation of the alloys by 1.66 and 1.43 times, respectively, compared to alloys without Ta.
Prior research indicates that the incorporation of Ta element can effectively enhance the properties of TiAl alloys. However, many of these studies have focused on the addition of high Ta content, which is not conducive to the engineering application of TiAl alloys due to the high cost and density of Ta elements. Considering that high Nb-TiAl alloys have a wide range of applications and that Nb and Ta ele...
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Jiang-shan Liang, Liao Mi, Hong-ze Fang, Xin Ding, Xian-fei Ding, Bao-hui Zhu, Rui-run Chen (2026). Effect of Ta addition on microstructure and mechanical properties of Ti46Al1.5Cr8Nb alloy. China Foundry. https://doi.org/10.1007/s41230-025-5004-2
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Frequently Asked Questions
What is the optimal Ta content in Ti46Al1.5Cr8Nb alloy for mechanical properties?
The optimal Ta content is 0.4 at.%, which yields a compressive strength of 2,434 MPa and a compressive strain of 33.1%.
How does Ta addition affect the microstructure of TiAl alloys?
Ta addition increases the content of α2 and B2 phases while decreasing γ phase, and refines the lamellar colony size from 160.65 μm to 94.44 μm.
What are the main mechanisms for property improvement with Ta addition?
The improvement is attributed to lamellar colony refinement, solid solution strengthening from Ta, and a reduction in the c/a ratio of the γ phase.
Why is Ta considered a promising alloying element for TiAl alloys?
Ta has a higher melting point and superior performance compared to Nb, including better grain refinement and oxidation resistance, making it effective in enhancing high-temperature properties.
What is the significance of the B2 phase in Ta-containing TiAl alloys?
The B2 phase content increases significantly with Ta addition, and its refinement contributes to the overall microstructure optimization and improved mechanical properties.
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