Tailoring microstructure and chemical composition of advanced γ-TiAl based alloys for improved creep resistance

Kastenhuber, Michael; Klein, Thomas; Clemens, Helmut; Mayer, Svea

doi:10.1016/j.intermet.2018.03.011

Cited by 68 publications

(39 citation statements)

References 48 publications

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“…It is well known that substitutional elements like Nb, Mo, Ta, and W as well as the interstitial elements such as C improve high temperature creep resistance of TiAl-based alloys [9][10][11][12][13]. The addition of carbon up to about 0.8 at.% contributes to precipitation strengthening through the formation of two types of fine carbides: cubic perovskite-type Ti 3 AlC (P-type) with needle-like morphology and hexagonal Ti 2 AlC (H-type) with plate-like morphology [12,[14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Comparative Study of Microstructure and Mechanical Properties of Two TiAl-Based Alloys Reinforced with Carbide Particles

2020

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Microstructure and mechanical properties of two TiAl-based alloys with nominal composition Ti-42.6Al-8.7Nb-0.3Ta-2.0C and Ti-41.0Al-8.7Nb-0.3Ta-3.6C (in at.%) were investigated and compared. The alloys were prepared by vacuum induction melting, followed by centrifugal casting. The as-cast samples were subjected to hot isostatic pressing and heat treatment consisting of solution annealing in β (Ti-based solid solution) phase field, cooling at a constant rate and stabilization annealing. The microstructure of the alloys consists of α2 (Ti3Al) + γ (TiAl) lamellar grains, single γ phase, coarse Ti2AlC particles, and irregular shaped α2 phase. The increase in the content of C at the expense of decreasing Al in the studied alloys affects solid-state phase transformation temperatures and leads to a decrease in size of grains and primary Ti2AlC particles, increase in the volume fraction of reinforcing carbide particles, decrease in the volume fraction of lamellar colonies, and widening of the grain boundaries. Long-term ageing at 800 °C has no effect on the grain size but leads to the formation of Ti4Al3Nb particles and increase in interlamellar spacing. The Vickers hardness, microhardness of lamellar grains, indentation nanohardness, and elastic modulus of the boundary γ phase decrease during ageing. The Ti-42.6Al-8.7Nb-0.3Ta-2.0C alloy shows improved creep resistance compared to that of Ti-41.0Al-8.7Nb-0.3Ta-3.6C and some reference TiAl-based alloys at a temperature of 800 °C and applied stress of 200 MPa.

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Section: Introductionmentioning

confidence: 99%

Comparative Study of Microstructure and Mechanical Properties of Two TiAl-Based Alloys Reinforced with Carbide Particles

2020

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“…However, owing to poor solubility of C in the β 0 -phase, an increase in the overall C content diminishes the nano-hardness of the β 0 -phase. Hence, C is said to be an α 2 -phase stabilizer [ 3 ].…”

Section: Effects Of Alloying Elements On Tial-based Alloysmentioning

confidence: 99%

“…Ti–Al based alloying systems with Si are identified at the α 2 /γ lamellar interfaces with precipitates of ζ-silicide (Ti 5 Si 3 ) known to be responsible for diminishing the dislocation mobility and interfacial stability [ 7 , 54 , 116 , 117 ]. Si addition of ~0.5 at.% results in the formation of fine Ti 5 Si 3 particles; while between 2.0-6.0 at.% of Si produces large Ti 5 Si 3 particles or whiskers nucleated at γ/γ and γ/α 2 interfacial sites [ 3 , 113 ]. This tends to align particles at the interface of lamellae, particularly for alloys that have low quantity of α 2 -phase after heat treatments in the dual-phase region.…”

Section: Characteristic Effects Of Silicon Additions In Tial Alloysmentioning

confidence: 99%

“…Recently, an innovative variety of beta-solidifying (β-solidifying) titanium aluminide (TiAl) alloys have been developed by several researchers dubbed TNM and TNM + alloys [ 1 , 2 , 3 , 4 , 5 , 6 ]. In contrast to the peritectic solidification pattern prone to segregation, these alloys produce fine-grained homogeneous structures by solidifying entirely through the disordered β-phase (A2 structure) having a body-centred cubic (BCC) lattice structure [ 4 , 7 , 8 , 9 , 10 , 11 ].…”

Section: Introductionmentioning

confidence: 99%

“…Microalloying elements additions of B, Si and C were added to act as nucleation agents in TNM alloys during solidification and phase transformations. Moreover, B has proven to be the most effective for grain refinement [ 8 , 12 , 23 ]; while C and Si were more suitable in improving the maximum operating temperatures of TNM alloys giving rise to a promising alloy subclass known as TNM + [ 1 , 3 , 4 ]. Another important phase (though it is minor) present in TNM alloys is the ω o -phase [ 7 , 24 ].…”

Section: Introductionmentioning

confidence: 99%

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Characteristic effects of alloying elements on β solidifying titanium aluminides: A review

Raji

Popoola

Pityana

2020

Heliyon

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The high strength-to-weight ratio property of titanium aluminide (TiAl) based intermetallic alloys makes researchers regard this type of material as a potential replacement for the heavier superalloys of nickel. These alloys have been applied as turbocharger wheels of automobile and turbine blades of aircraft engines. A much recent alloy type of TiAl called the TNM alloy has emerged and primarily amenable to mechanical working; while providing the best combinations of mechanical properties that could be achieved through manufacturing processes with subsequent heat treatments. This is attained by solidifying entirely through the disordered β-phase (A2 structure). Effects of major alloying elements such as strength improvement, microstructural stability and phase formation demand the understanding of these alloying elements addition in TiAl-based intermetallic alloys. This review paper aims at encapsulating several works regarding the effects of major alloying elements on β-solidifying TiAl-based alloys and summarizing the characteristic effects of Si for these types of alloys. An impetus for future works on these types of intermetallic TiAl-based alloys is also presented.

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Locally Adapted Microstructures in an Additively Manufactured Titanium Aluminide Alloy Through Process Parameter Variation and Heat Treatment

et al. 2022

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Electron beam powder bed fusion (PBF-EB/M) has been attracting great research interest as a promising technology for additive manufacturing of titanium aluminide alloys. However, challenges often arise from the processinduced evaporation of aluminum, which is linked to the PBF-EB/M process parameters. This study applies different volumetric energy densities during PBF-EB/M processing to deliberately adjust the aluminum contents in additively manufactured Ti-43.5Al-4Nb-1Mo-0.1B (TNM-B1) samples. The specimens are subsequently subjected to hot isostatic pressing (HIP) and a two-step heat treatment. The influence of process parameter variation and heat treatments on microstructure and defect distribution are investigated using optical and scanning electron microscopy, as well as X-ray computed tomography (CT). Depending on the aluminum content, shifts in the phase transition temperatures can be identified via differential scanning calorimetry (DSC). It is confirmed that the microstructure after heat treatment is strongly linked to the PBF-EB/M parameters and the associated aluminum evaporation. The feasibility of producing locally adapted microstructures within one component through process parameter variation and subsequent heat treatment can be demonstrated. Thus, fully lamellar and nearly lamellar microstructures in two adjacent component areas can be adjusted, respectively.

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Tailoring microstructure and chemical composition of advanced γ-TiAl based alloys for improved creep resistance

Cited by 68 publications

References 48 publications

Comparative Study of Microstructure and Mechanical Properties of Two TiAl-Based Alloys Reinforced with Carbide Particles

Comparative Study of Microstructure and Mechanical Properties of Two TiAl-Based Alloys Reinforced with Carbide Particles

Characteristic effects of alloying elements on β solidifying titanium aluminides: A review

Locally Adapted Microstructures in an Additively Manufactured Titanium Aluminide Alloy Through Process Parameter Variation and Heat Treatment

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