Formation mechanism of an α2 phase-rich layer on the surface of Ti-22Al-25Nb alloy
- 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, Journal Name: Materials Characterization Vol. 145; ISSN 1044-5803; ISSN MACHEX
- Country of Publication:
- United States
- Language:
- English
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