Key Takeaways & Executive Findings
- •• Ti45Al8Nb-0.6C alloy exhibits a creep life of 137 h at 800°C/200 MPa, with a ductile-brittle mixed fracture mode. • Dynamic in-situ precipitation of Ti3AlC phase enhances creep resistance by impeding dislocation motion and inducing defect structures. • Creep deformation triggers pronounced B2 phase formation, deformation twinning, lamellar coarsening, and stacking faults. • Extensive dynamic recrystallization during creep leads to fine recrystallized grains, contributing to improved creep performance.
Abstract
TiAl alloys are attractive for high-temperature structural applications, yet their creep resistance and microstructural stability at high temperatures remain critical challenges. In this study, Ti45Al8Nb-0.6C alloy was prepared by vacuum induction melting to investigate its creep behavior and underlying deformation mechanisms at 800 °C under 200 MPa. The alloy exhibits a relatively homogeneous microstructure composed of (γ+α2) lamellar colonies, B2 phase, and blocky γ phase, with a creep life of 137 h and a typical ductile-brittle mixed fracture mode. Post-creep microstructural characterization reveals pronounced B2 phase formation, deformation twinning, lamellar coarsening, and abundant stacking faults at lamellar interfaces. Extensive dynamic recrystallization occurs during creep, leading to the formation of fine recrystallized grains. The Ti3AlC phase plays a dual strengthening role by effectively impeding dislocation motion and developing characteristic defect structures, including high-density dislocations and ladder-like stacking faults during deformation. These synergistic microstructural evolutions contribute to the enhanced creep resistance of the alloy.
1. Introduction
TiAl-based intermetallic alloys have emerged as promising lightweight structural materials for aerospace applications due to their exceptional combination of high specific strength, superior oxidation resistance, and excellent high-temperature mechanical properties [1-4]. A significant milestone in commercialization is achieved with the successful implementation of Ti-48Al-2Cr-2Nb alloy in GEnx™ engine low-pressure turbine (LPT) blades, demonstrating its engineering viability for critical rotating components [5]. The growing demand for next-generation aeroengines with higher thrust-to-weight ratios, extended service life, and improved fuel efficiency has driven intensive research on developing advanced TiAl alloys with enhanced high-temperature capabilities [6]. However, broader applications of these alloys remain constrained by their limited high-temperature strength and creep resistance under extreme service conditions [7].
Recent advances in microstructure engineering have revealed that near-lamellar microstructures exhibit particularly outstanding high-temperature strength and creep performance [8-10]. These specially designed microstructures maintain adequate ductility while effectively impeding dislocation motion and grain boundary sliding at elevated temperatures, offering new opportunities for developing next-generation high-performance TiAl alloys.
Alloying has been widely recognized as an effective strategy for enhancing the properties of TiAl-based alloys [11-14]. Zhou et al. [15] developed Ti-46Al-2.6C-xNb [x=(0-4)at.%] alloys using ultrasonic-assisted vacuum arc remelting (VAR). Their results demonstrated that increasing the Nb content from 0 to 4at.% significantly improved the ultimate compressive strength from 2,074 MPa to 2,474 MPa and concurrently increased the fracture strain from 23% to 28%. In a complementary study, Wang et al. [16] successfully fabricated Ti-45Al-8Nb alloy using arc-directed energy deposition (DED), revealing that Nb addition not only effectively reduced internal defects but also substantially enhanced mechanical properties through combined solid solution strengthening, grain refinement, and dislocation strengthening effects when compared with binary Ti-45Al alloy. These findings collectively highlight the crucial role of Nb alloying in optimizing both the processing characteristics and mechanical performance of TiAl alloys.
Although Nb is an effective β-stabilizing element in TiAl alloys, excessive addition can promote the formation of brittle B2 phase, leading to reduced ductility [17-19]. Recent studies [20, 21] have shown that this detrimental effect can be counteracted by incorporating α-stabilizing elements such as carbon. Beyond compensating for the negative impact of β-stabilizers, carbon addition independently enhances TiAl alloy performance through multiple mechanisms [22]. Carbon exhibits limited solid solubility in TiAl alloys, and when its content exceeds ~0.5at.%, it preferentially forms Ti2AlC (H-phase) and Ti3AlC (P-phase) [23, 24]. Li et al. [25] systematically investigated this phenomenon in Ti-43Al-6Nb-1Mo-1Cr-xC [x=(0...
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Zhe Deng, Pei Liu, Wei Wang, Ai-qin Wang, Jing-pei Xie, Zhi-yong Zhang (2026). Regulating creep behavior via dynamic in-situ precipitation of Ti3AlC phase in Ti45Al8Nb-0.6C alloy. China Foundry. https://doi.org/10.1007/s41230-026-5201-7
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Frequently Asked Questions
What is the creep life of Ti45Al8Nb-0.6C alloy at 800°C under 200 MPa?
The alloy exhibits a creep life of 137 hours under these conditions.
What is the role of Ti3AlC phase in enhancing creep resistance?
Ti3AlC phase impedes dislocation motion and develops characteristic defect structures, such as high-density dislocations and ladder-like stacking faults, contributing to enhanced creep resistance.
What microstructural changes occur during creep of Ti45Al8Nb-0.6C alloy?
Post-creep characterization reveals pronounced B2 phase formation, deformation twinning, lamellar coarsening, abundant stacking faults, and extensive dynamic recrystallization leading to fine recrystallized grains.
How was the Ti45Al8Nb-0.6C alloy prepared?
The alloy was prepared by vacuum induction melting.
What is the fracture mode of the alloy after creep?
The alloy exhibits a typical ductile-brittle mixed fracture mode.
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