Formation mechanism of an α2 phase-rich layer on the surface of Ti-22Al-25Nb alloy

Journal Article · Thu Nov 15 00:00:00 EST 2018 · Materials Characterization

DOI:https://doi.org/10.1016/J.MATCHAR.2018.08.030· OSTI ID:22833010

Shao, Bin; Wan, Shengxiang; Xu, Wenchen; Shan, Debin; Guo, Bin; Zong, Yingying ^[1]

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1. State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001 (China)

Highlights: • This paper reports the formation mechanism of a α{sub 2}-rich layer on the surface of the Ti-22Al-25Nb alloy. • The α{sub 2}-rich layer is significantly harder than the alloy interior. • The α{sub 2}-rich layer is formed owing to the Ti{sub 2}O{sub 3} particles produced by oxygen infiltration at the surface. • The relative orientation of the α{sub 2} and Ti{sub 2}O{sub 3} phases is (1–100)α{sub 2}//(1–100)Ti{sub 2}O{sub 3}. - Abstract: In order to investigate the formation mechanism of the α{sub 2}-rich layer in the surface of the Ti-22Al-25Nb alloy, systematic analyses are carried out on the surface of the alloy by using SEM, XRD and EBSD. The results reveal that this α{sub 2}-rich layer is formed by oxidation of the surface layer. In this surface oxidation layer, there are abundant Ti{sub 2}O{sub 3} particles similar with the α{sub 2} phase in structure. These Ti{sub 2}O{sub 3} particles serve as nucleation points and lower the nucleation energy of the α{sub 2} phase, promoting the precipitation and growth of α{sub 2} phase on the surface layer of the alloy. This surface layer has a hardness of 684 HV, significantly exceeding the value of 312 HV for the interior of the alloy and thus considerably improves the surface properties of the alloy, serving as a high-performance, self-generated surface strengthening layer.

• OSTI ID: 22833010
• Journal Information: Materials Characterization, Vol. 145; Other Information: Copyright (c) 2017 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 1044-5803
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM COMPOUNDS
BACKSCATTERING
ELECTRON DIFFRACTION
HARDNESS
LAYERS
NIOBIUM COMPOUNDS
NUCLEATION
OXIDATION
PHASE TRANSFORMATIONS
PRECIPITATION
SCANNING ELECTRON MICROSCOPY
SURFACE PROPERTIES
SURFACES
TERNARY ALLOY SYSTEMS
TITANIUM COMPOUNDS
X-RAY DIFFRACTION