Grain refinement of 1 at.% Ta-containing cast TiAl-based alloy by cyclic air-cooling heat treatment

Zhang, Keren; Hu, Rui; Li, Jinguang; Yang, Jieren; Gao, Zitong

doi:10.1016/j.matlet.2020.127940

Cited by 22 publications

(4 citation statements)

References 24 publications

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“…According to previous studies [32][33][34], the addition of Ta to TiAl alloys can improve their mechanical properties, including their tensile strength, compressive strength and hardness, due to solution strengthening and refinement of the massive γ phase by controlling metastable microstructural evolution [35][36][37]. Ta and Nb elements can extend the cooling rate requirement for the α → γ m massive transformation to avoid the quenching of cracks caused by an excessive cooling rate [38].…”

Section: Introductionmentioning

confidence: 99%

Effects of Thermal Exposure on the Microstructure and Mechanical Properties of a Ti–48Al–3Nb–1.5Ta Alloy via Powder Hot Isostatic Pressing

Zuo,

Hu,

Wang

et al. 2024

Materials

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Research on how thermal exposure affects the microstructure and mechanical properties of the Ti–48Al–3Nb–1.5Ta (at. %) alloy, which is prepared via powder hot isostatic pressing (P–HIP), is essential since this low-density alloy shows promise for use in high-temperature applications, particularly for aero-engines, which require long-term stable service. In this study, a P–HIP Ti–48Al–3Nb–1.5Ta (at. %) alloy was exposed to high temperatures for long durations. The phase, microstructure and mechanical properties of the P–HIP Ti–48Al–3Nb–1.5Ta alloy after thermal exposure under different conditions were analyzed using XRD, SEM, EBSD, EPMA, TEM, nanomechanical testing and tensile testing. The surface scale is composed of oxides and nitrides, primarily Al2O3, TiO2, and TiN, among which Al2O3 is preferentially generated and then covered by rapidly growing TiO2 as the thermal exposure duration increases. The nitrides appear later than the oxides and exist between the oxides and the substrate. With increasing exposure temperature and duration, the surface scale becomes more continuous, TiO2 particles grow larger, and the oxide layer thickens or even falls off. The addition of Ta and Nb can improve the oxidation resistance because Ta5+ and Nb5+ replace Ti4+ in the rutile lattice and weaken O diffusion. Compared with the P–HIP Ti–48Al–3Nb–1.5Ta alloy, after thermal exposure, the grain size does not increase significantly, and the γ phase increases slightly (by less than 3%) with the decomposition of the α2 phase. With increasing thermal exposure duration, the γ phase exhibits discontinuous coarsening (DC). Compared with the P–HIP Ti–48Al–3Nb–1.5Ta alloy, the hardness increases by about 2 GPa, the tensile strength increases by more than 50 MPa, and the fracture strain decreases by about 0.1% after thermal exposure. When the depth extends from the edge of the thermally exposed specimens, the hardness decreases overall.

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Section: Introductionmentioning

confidence: 99%

Effects of Thermal Exposure on the Microstructure and Mechanical Properties of a Ti–48Al–3Nb–1.5Ta Alloy via Powder Hot Isostatic Pressing

Zuo,

Hu,

Wang

et al. 2024

Materials

Self Cite

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“…In addition, significant nanohardness was observed at 10.57 ± 0.53 GPa, a higher value compared to conventionally produced TiB 2 reinforced TiAl alloy. With respect to microstructural refinement, an alloying element such as Ta is very effective, which consequently enhances tensile strength and plasticity when added to a TiAl alloy [ 24 , 25 , 26 ]. Meanwhile, reinforcing with nitride particles has been proven to impact superior mechanical properties and to be an efficient reinforcing material for TiAl alloys [ 19 ].…”

Section: Introductionmentioning

confidence: 99%

Nanoindentation and Structural Analysis of Sintered TiAl(100−x)-xTaN Composites at Room Temperature

2023

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The nanohardness, elastic modulus, anti-wear, and deformability characteristics of TiAl(100−x)-xTaN composites containing 0, 2, 4, 6, 8, and 10 wt.% of TaN were investigated via nanoindentation technique in the present study. The TiAl(100−x)-xTaN composites were successfully fabricated via the spark plasma sintering technique (SPS). The microstructure and phase formation of the TiAl sample constitute a duplex structure of γ and lamellar colonies, and TiAl2, α-Ti, and TiAl phases, respectively. The addition of TaN results in a complex phase formation and pseudo duplex structure. The depth-sensing indentation evaluation of properties was carried out at an ambient temperature through a Berkovich indenter at a prescribed load of 100 mN and a holding time of 10 s. The nanoindentation result showed that the nanohardness and elastic modulus characteristics increased as the TaN addition increased but exhibited a slight drop when the reinforcement was beyond 8 wt.%. At increasing TaN addition, the yield strain (HEr), yield pressure (H3Er2), and elastic recovery index (WeWt) increased, while the plasticity index (WpWt) and the ratio of plastic and elastic work (RPE) reduced. The best mechanical properties were attained at the 8 wt.%TaN addition.

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“…Thus, the microstructure can also be refined by hot deformation. The microstructure refinement is conductive to the improvement in ductility [8,9]. However, the β phase transforms into the ordered β 0 phase with high hardness below 1100 • C [10].…”

Section: Introductionmentioning

confidence: 99%

Microstructural Characterization and Crack Propagation Behavior of a Novel β-Solidifying TiAl Alloy

Zhang

Cui

Sun

et al. 2021

Metals

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Novel β-solidifying TiAl alloys have great potential for engineering applications in the aerospace and automotive industries. The introduction of the β0 phase will inevitably affect crack propagation. However, the related mechanism is unclear. In this study, the crack propagation behavior of different β0-containing microstructures was systematically investigated by three-point bending tests. The results show that the coarse γ/α2 lamellar microstructure exhibits better fracture toughness than the fine-grain microstructure because large numbers of γ/α2 lamellar boundaries can effectively hinder crack propagation. The propagation direction depends largely on the orientation of the γ/α2 lamellae. When the angle between the crack propagation direction and the γ/α2 lamellar boundary is small, the crack tends to propagate along γ/α2 lamellae. When the angle is close to 90°, the crack generally propagates by the trans-lamellar mode. Moreover, the crack tends to traverse across the fine β0/γ duplex region due to the low resistance of fine grains in the crack propagation. The transgranular and intergranular modes are the main fracture mechanisms in the microstructure of the fine β0/γ grains. Some shear ligaments can also be identified in the lamellar microstructure and these can consume propagation energy. The enlarged image shows that the crack propagation direction can be changed by the β0 phase, owing to its high hardness. The crack tends to stop at the β0 phase region.

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Grain refinement of 1 at.% Ta-containing cast TiAl-based alloy by cyclic air-cooling heat treatment

Cited by 22 publications

References 24 publications

Effects of Thermal Exposure on the Microstructure and Mechanical Properties of a Ti–48Al–3Nb–1.5Ta Alloy via Powder Hot Isostatic Pressing

Effects of Thermal Exposure on the Microstructure and Mechanical Properties of a Ti–48Al–3Nb–1.5Ta Alloy via Powder Hot Isostatic Pressing

Nanoindentation and Structural Analysis of Sintered TiAl(100−x)-xTaN Composites at Room Temperature

Microstructural Characterization and Crack Propagation Behavior of a Novel β-Solidifying TiAl Alloy

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