Investigation of the phase transformations in Ti 22Al 25Nb alloy

Shao, Bin; Zong, Yingying; Wen, Daosheng; Tian, Yingtao; Shan, Debin

doi:10.1016/j.matchar.2016.02.011

Cited by 82 publications

(16 citation statements)

References 20 publications

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“…3(a) . The lamellar α 2 phase spheroidizes and grows during the tensile process 22 , and the rich α 2 phase layer tears during the tensile process, as shown in Fig. 3(b) .…”

Section: Resultsmentioning

confidence: 98%

The formation mechanism of tear strips on stretched Ti-22Al-25Nb alloy sheets

Zong

Shao

Wang

et al. 2017

Sci Rep

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This paper reports the presence of tear strips on the surface of a Ti-22Al-25Nb alloy sheet stretched at 960 °C. The test piece reveals a "bamboo"-shaped pattern on its surface, which severely affects the quality of the alloy. Microstructure analysis indicates that the formation mechanism of the tear strip is related to both the rich α 2 phase layer and the interfacial B2 phase dynamic recrystallization layer between the α 2 phase layer and the substrate metal.Ti-22Al-25Nb alloy is a second-generation Ti 2 AlNb-based alloy 1 that is composed of a body-centred cubic B2 phase, an orthogonal structure O phase, and a hexagonal closely packed α 2 phase. The B2 phase is the substrate of the alloy and is vulnerable to sliding deformation, demonstrating good plastic deformation 2, 3 . The O and α 2 phases strengthen the alloy. The Ti-22Al-25Nb alloy is characterized by high strength, light weight, and high temperature resistance and is a new generation of aerospace structure material [4][5][6] . However, its extensive application has proven challenging due to difficulties in its hot forming. Therefore, a large number of studies have been conducted to study the tensile, compressive and processing properties of the Ti-22Al-25Nb alloy [7][8][9][10] . The research results reveal good plastic deformation capability of this alloy at temperatures greater than 950 °C 11 . In general, the elongation rate exceeds 80%, and the deformation resistance is smaller than 200 MPa 12 . In addition, dynamic recrystallization is observed during the deformation of this alloy 13,14 . The alloy is suitable for hot forming under such conditions 10,[15][16][17] . Most forming devices do not have a good protection environment in real production processes, which leads to oxidation of this alloy at elevated temperature, generating oxides such as TiO 2 , AlNbO 4 , and Al 2 O 3 . Oxidation results in a sequence of surface defects, such as surface roughness and cracking, affecting the surface quality of the alloy 18,19 . The Ti-22Al-25Nb alloy is primarily used in aviation spacecraft in the form of sheet metal, such as mounting frames for insulation and the exterior surface 20,21 . The surface quality of the metal sheet is an important quality indicator of the workpiece. Thus, it is important to determine the surface defects during the forming process and to develop ways to avoid surface defects and improve the surface quality of the alloy components. Materials and Experimental ProceduresThe material used in this report was a 1 mm thick Ti-22Al-25Nb alloy sheet. The tensile test was performed with an Instron-5500R electronic universal testing instrument. The gauge length and width of the tensile test piece were 20 mm and 5 mm, respectively, as shown in Fig. 1(b). The stretching temperature was 960 °C, and the strain rates were 0.0025/s, 0.025/s, and 0.25/s. Before stretching, heat preservation was performed for 15 min, and water cooling after the fracture process maintained the tensile structure. The specimen was then polished by electrolysis for micr...

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“…3(a) . The lamellar α 2 phase spheroidizes and grows during the tensile process 22 , and the rich α 2 phase layer tears during the tensile process, as shown in Fig. 3(b) .…”

Section: Resultsmentioning

confidence: 98%

The formation mechanism of tear strips on stretched Ti-22Al-25Nb alloy sheets

Zong

Shao

Wang

et al. 2017

Sci Rep

Self Cite

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“…The phase transition of O ! B2 occurs during 960-990 C, [21] which is the other reason of the alloy having lower deformation resistance and higher elongation apart from B2 phase dynamic recrystallization.…”

Section: Resultsmentioning

confidence: 99%

“…At 990 °C, degree of dynamic recrystallization is enhanced, and the number of α 2 phase and O phase decreases significantly (Figure c,d). The phase transition of O → B2 occurs during 960–990 °C, which is the other reason of the alloy having lower deformation resistance and higher elongation apart from B2 phase dynamic recrystallization.…”

Section: Resultsmentioning

confidence: 99%

Deformation Behavior and Dynamic Recrystallization of Ti–22Al–25Nb Alloy at 750–990 °C

et al. 2019

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Ti-22Al-25Nb is a representative of Ti 2 AlNb alloys with excellent comprehensive properties, which has great application prospects in the aerospace field. Herein, high-temperature tensile plastic deformation behavior and dynamic recrystallization process of Ti-22Al-25Nb alloy are researched during 750-990 C. From 750 to 870 C, plasticity is gradually improved with temperature increasing, and the fracture mode is crack aggregation. From 900 to 930 C, the content of B2 phase increases and plasticity is significantly improved because crack along the grain is suppressed by combined precipitation of three phases B2 þ O þ α 2 at grain boundaries with large areas. From 960 to 990 C, the alloy is mainly composed of B2 phase and has best plastic deformation performance. Fully dynamic recrystallization of B2 phase happens at 990 C. Texture strength is strengthened by intense plastic deformation, but it is weakened by dynamic recrystallization subsequently.

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“…Especially, the constitutive behavior of Ti 2 AlNb-based alloys can be affected by various factors such as temperature, strain rate, and strain. [3][4][5] Constitutive models express the effect of deformation temperature, strain rate, and strain on flow stress, with which the flow stress evolution of metallic alloys at ambient or elevated temperature can be described effectively. [6,7] In consequence, they are of great importance for the finite element (FE) simulation, design, and control of thermomechanical processing for metallic alloys.…”

Section: Introductionmentioning

confidence: 99%

Constitutive Modeling of a Fine‐Grained Ti₂AlNb‐Based Alloy Fabricated by Mechanical Alloying and Subsequent Spark Plasma Sintering

Sim¹,

Li²,

Li³

et al. 2020

Adv Eng Mater

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The flow stress evolution of a fine-grained Ti 2 AlNb-based alloy fabricated by mechanical alloying and subsequent spark plasma sintering is experimentally acquired for different deformation conditions. Isothermal uniaxial compression test is conducted in the deformation temperature range of 950-1070 C and the strain rate range of 0.001-1 s À1. Based on the experimental flow stress with friction correction, the modified Johnson-Cook model and strain-compensated Arrhenius-type model are established in the α 2 þ β/B2 þ O triple-phase and α 2 þ B2 two-phase fields. The average absolute relative error (AARE) and determination coefficient (R 2) are 9.78% and 0.9858 for the modified Johnson-Cook model, and 4.19% and 0.9927 for the strain-compensated Arrhenius-type model. Compared with the modified Johnson-Cook model, the straincompensated Arrhenius-type model is more suitable for predicting the hightemperature flow stress of a fine-grained Ti 2 AlNb-based alloy fabricated by mechanical alloying and subsequent spark plasma sintering.

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Investigation of the phase transformations in Ti 22Al 25Nb alloy

Cited by 82 publications

References 20 publications

The formation mechanism of tear strips on stretched Ti-22Al-25Nb alloy sheets

The formation mechanism of tear strips on stretched Ti-22Al-25Nb alloy sheets

Deformation Behavior and Dynamic Recrystallization of Ti–22Al–25Nb Alloy at 750–990 °C

Constitutive Modeling of a Fine‐Grained Ti₂AlNb‐Based Alloy Fabricated by Mechanical Alloying and Subsequent Spark Plasma Sintering

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Investigation of the phase transformations in Ti 22Al 25Nb alloy

Cited by 82 publications

References 20 publications

The formation mechanism of tear strips on stretched Ti-22Al-25Nb alloy sheets

The formation mechanism of tear strips on stretched Ti-22Al-25Nb alloy sheets

Deformation Behavior and Dynamic Recrystallization of Ti–22Al–25Nb Alloy at 750–990 °C

Constitutive Modeling of a Fine‐Grained Ti2AlNb‐Based Alloy Fabricated by Mechanical Alloying and Subsequent Spark Plasma Sintering

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Constitutive Modeling of a Fine‐Grained Ti₂AlNb‐Based Alloy Fabricated by Mechanical Alloying and Subsequent Spark Plasma Sintering