Influence of duplex ageing on secondary α precipitates and mechanical properties of the near β-Ti alloy Ti-55531

Journal Article · Mon Oct 15 04:00:00 EDT 2018 · Materials Characterization

DOI:https://doi.org/10.1016/J.MATCHAR.2018.06.025· OSTI ID:22805770

Ren, Lei; Xiao, Wenlong ^[1]; Han, Weizhong ^[2]; Ma, Chaoli ^[1]; Zhou, Lian ^[1]

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1. Key Laboratory of Aerospace Advanced Materials and Performance of Ministry of Education, School of Materials Science and Engineering, Beihang University, Beijing 100191 (China)
2. State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049 (China)

Highlights: • High strength β-Ti alloys are widely used for their excellent properties. • To reach an excellent combination of strength and ductility, it is attractive to explore the right heat treatment system. • While compared to the conventional single-step ageing process, duplex ageing could change the development and refinement of secondary α precipitations in near/metastable β-Ti alloys resulting varying in performance. • Therefore it is of scientific significance and engineering value to understand the influence of duplex ageing on the formation of secondary α precipitates and mechanical properties for this type of alloy. - Abstract: This paper presents the results of studies on the microstructure and mechanical properties of a near β-Ti alloy processed with different ageing approaches. Influences of intragranular ultrafine α precipitates and grain boundary α layer on mechanical properties in Ti-55531 alloy were analyzed. The results indicate that the precipitation microstructure of the duplex aged alloy exhibits a uniform size and acicular α precipitated orientation shows an angle of approximately 60°. While the morphology of secondary α precipitates in single-step aged samples appear the irregular distribution and heterogeneous size. With the final ageing time increasing, the morphology of intragranular α precipitates and grain boundary α phase brings out a distinct coarsening. The single-step aged alloy can yield a better combination of the ultimate tensile strength (1265 MPa) and ductility (9%). However, the ultimate tensile strength of the duplex aged alloy even reaches 1368 MPa but it breaks at the stage of elastic deformation. The fracture mode of Ti-55531 alloy changes from predominantly dimple fracture in single-step aged samples to predominantly faceted and cleavage type fracture in duplex aged samples causing by the differences of intragranular α precipitates and the interface between grain boundary α layer and intragranular microstructure.

• OSTI ID: 22805770
• Journal Information: Materials Characterization, Journal Name: Materials Characterization Vol. 144; ISSN 1044-5803; ISSN MACHEX
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
AGING
DISTRIBUTION
DUCTILITY
ELASTICITY
FRACTURES
GRAIN BOUNDARIES
HEAT TREATMENTS
LAYERS
PRECIPITATION
PRESSURE RANGE GIGA PA
TITANIUM ALLOYS