Microstructure and Mechanical Properties of TC11 Titanium Alloy Fabricated by Wire-feed Electron Beam Additive Manufacturing

doi:10.3901/JME.2023.04.105

Abstract

Abstract: In this study, a α+β high-temperature titanium alloy TC11 ring (f260 mm) was fabricated by wire-feed electron beam additive manufacturing (EBAM). The microstructure, tensile property and the anisotropy of the tensile properties of the fabricated alloy were investigated. The microstructure and tensile property of the wrought alloy and the wrought + additive manufacturing interface were also evaluated. Optical microscopy, scanning electron microscopy, transmission electron microscopy and X-ray diffraction were employed to study the microstructure characteristics. The tensile properties along the vertical (V) and horizontal (H) directions were evaluated at both room temperature and 500 ℃. Results indicated that the microstructure of the as-built alloy was characterized by coarse columnar grains, lamellar α (colony and basket-weave), and the continuous grain boundary α. The prior β grains had a strong <001>_βtexture along the grain growth direction. Compared to the as-built alloy, the lamellar α phase was coarsened from 1.1 μm to 1.8 μm, the discontinuous grain boundary α and bi-lamellar α phase formed by post-deposition heat treated at 950 ℃/2 h/AC+530 ℃/6 h/AC. The equiaxed primary α of the wrought substrate alloy changed from globular to snowflake near the interface. After heat treatment, the volume fraction of the transformed β decreased for the wrought substrate alloy. In terms of tensile properties, the vertical specimens exhibited lower strength but higher ductility than the horizontal specimens at both room and elevated temperatures. The anisotropic elongation results from the directional columnar prior β grains and continuous grain boundary α phase, which facilitated the intergranular cracking. The tensile strength and ductility were simultaneously enhanced by the heat treatment to meet the standard requirements for wrought counterparts. Moreover, the anisotropy of the tensile strength and elongation for the post-deposition heat treated alloy was decreased significantly from 4.4% and 27.1% to 1.6% and 5.4%, respectively, in comparison to the as-built alloy. The tensile property of the wrought+additive manufacturing interface can meet the standard requirements for wrought counterparts.

Key words: titanium alloy, electron beam, additive manufacturing, microstructure, mechanical property, anisotropy

CLC Number:

TG146

ZHANG Guodong, ZHANG Peng, GAO Jianshi, YU Huai, YUAN Hong, DING Ning, XIONG Huaping. Microstructure and Mechanical Properties of TC11 Titanium Alloy Fabricated by Wire-feed Electron Beam Additive Manufacturing[J]. Journal of Mechanical Engineering, 2023, 59(4): 105-112.

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