High-temperature strengthening mechanisms of Laves and B2 precipitates in a novel ferritic alloy

Journal Article · Wed Feb 07 00:00:00 EST 2018 · Materials Science and Engineering. A, Structural Materials: Properties, Microstructure and Processing

DOI:https://doi.org/10.1016/j.msea.2018.02.013· OSTI ID:1465062

Chen, Tianyi ^[1]; Parish, Chad M. ^[1]; Yang, Ying ^[1]; Tan, Lizhen ^[1]

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1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Precipitates of the Laves and B2 phases were engineered in a newly-designed advanced ferritic alloy. Under creep test at 650 °C with 120 MPa, the material showed a steady-state minimum creep rate of 1 × 10^–4 h^–1, about one order of magnitude lower than T91. Microstructural characterization of the ferritic alloy revealed primarily ductile and partially brittle fractures after the creep test. Coarse Laves phase (~ 1 µm) was observed associating with the brittle fracture, resulting in reduced creep ductility. However, fine Laves phase precipitates (~ 100 nm) helped the dimple-ductile fracture and strengthened the material through impeding the motion of dislocations and boundaries. Unlike the B2 precipitates remained coherent exerting the classic Orowan bypassing mechanism at the brittle location, some of the B2 precipitates at the ductile location became incoherent and can develop an attractive interaction with dislocations. In conclusion, this coherency change of B2 precipitates, together with the nucleation of ultrafine (~ 40 nm) Laves phase precipitates during the creep test, would compensate for the coarsening-induced loss of Orowan strengthening of coherent B2 precipitates.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 1465062
• Alternate ID(s): OSTI ID: 22829402
• Journal Information: Materials Science and Engineering. A, Structural Materials: Properties, Microstructure and Processing, Journal Name: Materials Science and Engineering. A, Structural Materials: Properties, Microstructure and Processing Journal Issue: C Vol. 720; ISSN 0921-5093
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
Creep
Dislocation
Fracture
Microstructure
Orowan strengthening
Precipitation strengthening