Phase equilibria and microstructure on γ′ phase in Co-Ni-Al-W system

Kazuya Shinagawa, Toshihiro Omori, Jun Sato, Katsunari Oikawa, Ikuo Ohnuma, Ryosuke Kainuma, Kiyohito Ishida

Research output: Contribution to journalArticlepeer-review

270 Citations (Scopus)


Phase equilibria between the γ and γ′ phases at 900°C in the Co-(10-70)Ni-Al-W system were determined by electron probe microanalysis (EPMA) and X-ray diffractometry (XRD). It was found that the γ′ phase with L12 structure continuously exists from the Co side to the Ni side in Co-Ni-Al-W system and that it widens to the low W region with increasing Ni content. The partition of Al into the γ′ phase increased with Ni content, while the W changed from a γ′ former to a γ former by increase of Ni content. Differential scanning calorimetry (DSC) measurements also revealed that the γ′ solvus temperature increases with Ni content, while the solidus temperature is hardly affected by such content. The lattice parameter of the γ and γ′ phases and the mismatch decreased with increasing Ni content, which caused the morphologic change of the γ′ precipitates from cubes to spheres.

Original languageEnglish
Pages (from-to)1474-1479
Number of pages6
JournalMaterials Transactions
Issue number6
Publication statusPublished - 2008 Jun


  • Cobalt-nickel-aluminum-tungsten
  • LI compound
  • Lattice parameter
  • Phase equilibria
  • Phase stability
  • Superalloy


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