Thermal stability of bimodal grain structure in a cobalt-based superalloy subjected to high-temperature exposure

Li, Cheng Lin; Oh, Jeong Mok; Choi, Sunwoong; Mei, X.M.; Hong, Jae‐Keun; Yeom, Jong‐Taek; Mei, Q.S.; Yu, Zhentao; Park, Chan Hee

doi:10.1007/s12598-020-01627-7

Cited by 5 publications

(2 citation statements)

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“…Because microstructural evolution such as grain size change, [2,7,8] precipitate formation, [5,[9][10][11][12][13] and phase transformation [14][15][16] occur in CCWN alloys during thermomechanical treatment, it is essential to understand the role of microstructural evolution in improving the mechanical properties of the alloys through microstructural control. [15,[17][18][19][20][21][22][23][24] Ueki et al [17] designed alloys that can achieve high ductility by low-temperature heat treatment (LTHT) at 873 K in addition to high strength by grain refinement via static recrystallization. Improvement of ductility by LTHT has also been reported in biomedical Co-27Cr-6Mo alloys (mass pct).…”

Section: Introductionmentioning

confidence: 99%

“…Improvement of ductility by LTHT has also been reported in biomedical Co-27Cr-6Mo alloys (mass pct). [25] Li et al [19][20][21][22][23] achieved high strength in CCWN alloys through the formation of a bimodal grain structure. Moreover, they reported that a bimodal grain structure can be formed by performing cold rolling and static recrystallization five times, resulting in high strength and high ductility.…”

Section: Introductionmentioning

confidence: 99%

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Development of Low-Yield Stress Co–Cr–W–Ni Alloy by Adding 6 Mass Pct Mn for Balloon-Expandable Stents

Yanagihara

Ueki

Ueda

et al. 2021

Metall Mater Trans A

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This is the first report presenting the development of a Co–Cr–W–Ni–Mn alloy by adding 6 mass pct Mn to ASTM F90 Co–20Cr–15W–10Ni (CCWN, mass pct) alloy for use as balloon-expandable stents with an excellent balance of mechanical properties and corrosion resistance. The effects of Mn addition on the microstructures as well as the mechanical and corrosion properties were investigated after hot forging, solution treatment, swaging, and static recrystallization. The Mn-added alloy with a grain size of ~ 20 µm (recrystallization condition: 1523 K, 150 seconds) exhibited an ultimate tensile strength of 1131 MPa, 0.2 pct proof stress of 535 MPa, and plastic elongation of 66 pct. Additionally, it exhibited higher ductility and lower yield stress while maintaining high strength compared to the ASTM F90 CCWN alloy. The formation of intersecting stacking faults was suppressed by increasing the stacking fault energy (SFE) with Mn addition, resulting in a lower yield stress. The low-yield stress is effective in suppressing stent recoil. In addition, strain-induced martensitic transformation during plastic deformation was suppressed by increasing the SFE, thereby improving the ductility. The Mn-added alloys also exhibited good corrosion resistance, similar to the ASTM F90 CCWN alloy. Mn-added Co–Cr–W–Ni alloys are suitable for use as balloon-expandable stents.

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