Damage mechanism of nickel-based creep-resistant alloys strengthened by the Laves phase at the grain boundary

Mitsuharu Yonemura, Masatoshi Mitsuhara

Research output: Contribution to journalArticle

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Abstract

This study proposes a design guideline for polycrystal Ni-based model alloys with high ductility and 100-MPa creep rupture strength beyond 800°C and 105h. These alloys are strengthened by both the precipitation of fine γ′ particles inside the grain and the Laves phase at the grain boundary. For investigating the damage mechanism, transformation from the non-equilibrium Laves phase to the σ phase at the grain boundary and formation of the equilibrium needle-like Laves phase inside the grain are promoted by increasing the Fe concentration. The rupture time of Fe-free alloys significantly increases because of the equilibrium Laves phase at the grain boundary owing to a suitable Mo equivalent. In particular, W addition can help achieve high-temperature creep strength. The precipitate-free zone (PFZ) is predominantly formed by prior migration at the grain boundary without precipitation. Creep rupture occurs at the precipitation/matrix interface in the PFZ. Therefore, transformation control from the Laves to the σ phase at the grain boundary suppresses creep degradation. Consequently, a Ni-based alloy with strength >100 MPa and rupture elongation >20% at 800°C and 105h is fabricated using Larson–Miller parameter conversion, and the alloy design guideline’s validity is confirmed.

Original languageEnglish
Pages (from-to)3247-3266
Number of pages20
JournalPhilosophical Magazine
Volume98
Issue number36
DOIs
Publication statusPublished - Dec 22 2018

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Laves phases
grain boundaries
nickel
damage
precipitates
creep rupture strength
grain formation
creep strength
polycrystals
ductility
needles
elongation
degradation
matrices

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics

Cite this

Damage mechanism of nickel-based creep-resistant alloys strengthened by the Laves phase at the grain boundary. / Yonemura, Mitsuharu; Mitsuhara, Masatoshi.

In: Philosophical Magazine, Vol. 98, No. 36, 22.12.2018, p. 3247-3266.

Research output: Contribution to journalArticle

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