Microstructure Evolution and Mechanical Response of Ti-(43-45)Al-4Nb-1Mo-0.2B Alloys During the Hot-Pack Rolling

doi:10.11900/0412.1961.2024.00076

Acta Metall Sin

2025, Vol. 61

Issue (11): 1603-1614 DOI: 10.11900/0412.1961.2024.00076

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Microstructure Evolution and Mechanical Response of Ti-(43-45)Al-4Nb-1Mo-0.2B Alloys During the Hot-Pack Rolling

WEI Beibei¹(

), TANG Bin¹^,², CHEN Xiaofei¹, ZHANG Xiang¹, ZHU Lei³, LIU Renci⁴, LI Jinshan¹^,²

1 State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, China
2 Chongqing Innovation Center, Northwestern Polytechnical University, Chongqing 401135, China
3 Shaanxi Key Laboratory of Electrical Materials and Infiltration Technology, School of Materials Science and Engineering, Xi'an University of Technology, Xi'an 710048, China
4 Shi -changxu Innovation Center for Advanced Materials, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China

Cite this article:

WEI Beibei, TANG Bin, CHEN Xiaofei, ZHANG Xiang, ZHU Lei, LIU Renci, LI Jinshan. Microstructure Evolution and Mechanical Response of Ti-(43-45)Al-4Nb-1Mo-0.2B Alloys During the Hot-Pack Rolling. Acta Metall Sin, 2025, 61(11): 1603-1614.

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Abstract

Slight variations in the Al content can considerably affect the solidification path of TiAl alloys. Consequently, these variations influence the location of phase regions during the hot deformation process of TiAl alloys. In this study, Ti-(43-45)Al-4Nb-1Mo-0.2B (TNM, atomic fraction, %) ingots were synthesized via arc melting and labeled as 43Al, 44Al, or 45Al depending on their Al contents. Subsequently, TNM sheets were fabricated via hot-pack rolling, and the influence of Al content on the microstructure evolution and mechanical properties of these sheets during the rolling process was systematically investigated.Results indicate that TNM alloys with different Al contents are located in different phase regions when deformed at 1250 ^oC. After preheating for 1 h, the 43Al alloy is mainly composed of equiaxed α/α₂ grains. In contrast, the 44Al alloy exhibits a unique core-shell-like structure with α₂/γ lamellar colonies in the core and α/α₂ grains surrounding it. Compared with the 44Al alloy, the 45Al alloy demonstrates a lamellar structure with larger α₂/γ lamellar colonies. Furthermore, the initial structure remarkably influences the microstructure evolution of TNM sheets during the rolling process and determines the final microstructure composition of these sheets. With increasing Al content, the microstructure of TNM sheets transitions from nearly lamellar to duplex, eventually tending toward a near-γ structure. Additionally, two types of α₂/γ lamellar colonies—newly formed and initially present—are observed in the 43Al and 45Al sheets, respectively. Owing to its unique core-shell-like structure, the 44Al sheet simultaneously contains both types of α₂/γ lamellar colonies. Furthermore, the mechanical properties of TNM sheets with different Al contents were tested at room temperature. Results show a gradual decrease in the tensile strength of TNM sheets with increasing Al content. The 43Al sheet exhibits the best performance, which is attributed to the presence of newly formed lamellar structures. Meanwhile, the 44Al and 45Al sheets develop fractures rapidly because of the increased, clustered, and abnormal growth of equiaxed γ grains or presence of residual α₂/γ lamellar colonies.

Key words: TNM alloy hot-pack rolling microstructure evolution α₂/γ lamellar colony tensile performance

Received: 12 March 2024

ZTFLH:

TG146

Fund: National Key Research and Development Program of China(2021YFB3702603);Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University(CX2023045)

Corresponding Authors: WEI Beibei, Tel: 18734890249, E-mail: wbb@mail.nwpu.edu.cn

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	WEI Beibei
	TANG Bin
	CHEN Xiaofei
	ZHANG Xiang
	ZHU Lei
	LIU Renci
	LI Jinshan

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https://www.ams.org.cn/EN/10.11900/0412.1961.2024.00076 OR https://www.ams.org.cn/EN/Y2025/V61/I11/1603

Fig.1 Schematic of the multi-pass hot pack rolling

Fig.2 Schematic of the position of SEM, EBSD, and tensile samples on the sheet (a) and dimension of tensile sample (unit: mm) (b) (ND—normal direction, RD—rolling direction, TD—transverse direction)

Fig.3 Microstructures (a-c), corresponding phase distributions and contents (d-f), and inverse pole figures (IPFs) (g-i) of 43Al-45Al alloy ingots
(a, d, g) 43Al (b, e, h) 44Al (c, f, i) 45Al

Table 1 Chemical compositions of 43Al-45Al alloy ingots measured by EDS

Fig.4 Microstructures of 43Al (a), 44Al (b), and 45Al (c) alloys preheating at 1250 ^oC for 1 h (Insets show the locally enlarged views)

Fig.5 Low (a, c, e) and high (b, d, f) magnified SEM images of 43Al (a, b), 44Al (c, d), and 45Al (e, f) alloy sheets

Fig.6 Room-temperature tensile curves (a) and mechanical properties (b) of 43Al-45Al alloy sheets

Fig.7 Tensile fracture surface morphologies with low (a, c, e) and high (b, d, f) magnifications of 43Al (a, b), 44Al (c, d), and 45Al (e, f) alloy sheets tested at room temperature

Fig.8 EBSD analyses of 43Al sheet
(a, b) band contrast map covered the orientation relationship between α₂ and γ (a) and corresponding inverse pole figure (IPF) (b)
(c) local phase map and corresponding pole figures (PFs) of new α₂/γ lamella of the rectangle area in Fig.8a

Fig.9 EBSD analyses of 44Al alloy sheet
(a, b) band contrast map covered the orientation relationship between α₂ and γ (a) and corresponding IPF (b) (c, d) local phase maps and corresponding PFs of new α₂/γ lamella (c) and residual α₂/γ lamella (d) in Fig.9a

Fig.10 EBSD analyses of 45Al alloy sheet
(a, b) band contrast map covered the orientation relationship between α₂ and γ (a) and corresponding IPF (b)
(c) local phase map and corresponding PFs of residual α₂/γ lamella of the rectangle area in Fig.10a

Fig.11 Phase diagram (a) and schematic of microstructure evolution during hot-pack rolling (b) of 43Al-45Al alloy

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