Influence of duplex ageing on secondary α precipitates and mechanical properties of the near β-Ti alloy Ti-55531
- Key Laboratory of Aerospace Advanced Materials and Performance of Ministry of Education, School of Materials Science and Engineering, Beihang University, Beijing 100191 (China)
- 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, Vol. 144; 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
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