As-cast microstructure characteristics dependent on solidification mode in TiAl-Nb alloys

Ding, Xianfei; Zhang, Liwei; He, Jie; Zhang, Fuqiang; Feng, Xin; Hu, Nan; Lin, Junpin; Kim, Young‐Won

doi:10.1016/j.jallcom.2019.151862

Cited by 32 publications

(16 citation statements)

References 15 publications

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“…2(a). The worm-like β-segregation in the dendrite central region and dark grey interdendritic solidification segregation (S-segregation) caused by peritectic solidification [14] are observed with 0.1% Ru addition, as shown in Fig. 2(b).…”

Section: As-cast Microstructurementioning

confidence: 81%

Effects of Ru content on phase transformation and compression property of cast TiAl alloys

et al. 2020

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Ruthenium (Ru) is a promising element to heighten the comprehensive mechanical properties of TiAl alloys. In the present study, the phase transformation during the cooling of Ti-47Al-2Cr-2Nb-xRu (x=0, 0.1, 0.5, 1.0, at.%) alloys was investigated. The results show that Ru tends to segregate in the interdendritic region during solidification, and therefore, refines the as-cast microstructure of the alloys. As a β-stabilizer, Ru does not induce a novel solidification reaction but maintains the peritectic reaction of L+β→α. An excessive Ru content would cause the formation of (γ+τ 1 +B2) and (α+γ+τ 1 +B2) phase regions below 1,250 °C. The precipitation of τ 1 -containing mixture is attributed to the Ru-segregation, which inhibits the reaction of α→γ and facilitates the formation of B2 phase. The discontinuous coarsening of γ phase and block τ 1 phase formed alternately in a manner of analogous eutectoid decomposition within B2 phase. In addition, the effect of Ru content on compression property of the alloys was studied. The yield strength increases up to 427 MPa at 800 °C with the addition of 1.0at.% Ru, which is mainly due to the solution strengthening effect of Ru.

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Section: As-cast Microstructurementioning

confidence: 81%

Effects of Ru content on phase transformation and compression property of cast TiAl alloys

et al. 2020

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“…In peritectic solidification, from (b,c), the peritectic reaction happens in which the phase envelop the dendrite. Then, from (d,e), the phase keeps growing through peritectic transformation [84]. In solidification, solid state transformation happens from (i-k).…”

Section: Ingot Metallurgymentioning

confidence: 99%

“…In β solidification, solid state transformation happens from (i-k). Reproduced from [84], with permission of Elsevier 2019.…”

Section: Powder Metallurgy and Compactionmentioning

confidence: 99%

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Microstructure Design and Its Effect on Mechanical Properties in Gamma Titanium Aluminides

Liu

Lin

Zhang

et al. 2021

Metals

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Intermetallic gamma titanium aluminides display attractive engineering properties at high temperatures of up to 750 °C. To date, they have been used in low-pressure turbine blades and turbocharger rotors in advanced aircraft and automotive engines. This review summarizes the fundamental information of the Ti–Al system. After providing the development of TiAl alloys, typical phases, microstructures and their characteristics in TiAl alloys, the paper focuses on the effects of alloying elements on the phase boundary shifting, stabilizing effects and strengthening mechanism. The relationships between chemical additions, microstructure evolution and mechanical properties of the alloy are discussed. In parallel, the processing technologies and the common heat treatment methods are described in detail, both of which are applied to optimize the mechanical properties via adjusting microstructures. On this basis, the effects from chemical composition, processing technologies and heat treatments on microstructure, which controls the mechanical properties, can be obtained. It has a certain guiding significance for tailoring the microstructures to gain desired mechanical properties.

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“…TiAl-based intermetallic alloys are promising high-temperature structural materials considered as a potential replacement for the existing Ni-based alloys in the aerospace and automotive industries because of their low density, high strength and stiffness, and good creep resistance at elevated temperatures. [1][2][3][4] The γ-TiAl intermetallics are used in low-pressure turbine blades in the engines of the Boeing 787 and Boeing 747-8 aircraft, which has created interest in the development of TiAl-based alloys. [5][6][7] Issues such as low ductility and fracture toughness at room temperature also need to be resolved.…”

Section: Introductionmentioning

confidence: 99%

Effects of Solidification Rates on Microstructure Refinement and Elemental Distribution of Ti44Al6Nb1.0Cr2.0V0.1B0.15Y Alloy by Rapid Solidification

et al. 2020

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In order to refine microstructure and improve mechanical properties, size of lamellar colonies and reinforced phase, distribution of elements, and microhardness with different solidification rates were studied by rapid solidification. Results show that microstructure morphology changes from equiaxed grain to granulated dendrites after rapid solidification. When speed of revolution increases, size of lamellar colonies decreases from 53.5 to 16.9 μm and length of TiB particles decreases from 60.1 to 20.4 μm. The B2 phase exists in lamellar colonies and at the boundary of lamellar colonies before rapid solidification and forms in lamellar colonies after rapid solidification. An increase in solidification rate increases degree of supercooling to increase number of nucleation particles which form before solidification front. The β phase incompletely transforms to the α phase and is retained in α phase after rapid solidification. The microstructure does not have enough time to transform completely and high‐temperature microstructure is retained at a higher cooling rate. Test results show that microhardness increases from 453 to 562 HV when speed of revolution increases from 0 to 800 rpm. Improvement of microhardness results from solution strengthening of Nb, Cr, and V, grain refinement strengthening and reduction of the reinforced phase of TiB.

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As-cast microstructure characteristics dependent on solidification mode in TiAl-Nb alloys

Cited by 32 publications

References 15 publications

Effects of Ru content on phase transformation and compression property of cast TiAl alloys

Effects of Ru content on phase transformation and compression property of cast TiAl alloys

Microstructure Design and Its Effect on Mechanical Properties in Gamma Titanium Aluminides

Effects of Solidification Rates on Microstructure Refinement and Elemental Distribution of Ti44Al6Nb1.0Cr2.0V0.1B0.15Y Alloy by Rapid Solidification

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