Investigations on the Phase Transformations, Equilibria and Athermal ω in Ni-Ga-Cr Ternary System

Jingjing Ruan, Yuyuan Chen, Kosei Kobayashi, Nobufumi Ueshima, Katsunari Oikawa

Research output: Contribution to journalArticlepeer-review


In the present work, the phase equilibria of the Ni-Ga-Cr ternary system at 850, 1000 and 1150 °C were experimentally investigated to provide the essential data for developing the high-entropy shape memory alloys (HESMAs) containing Ni, Ga and Cr. At 850 °C, in the Ni-rich portion, the B2 phase shows equilibrium with the L12 phase when the Cr content is less than 10.49 at. %, while displaying the equilibrium with L12 and BCC phases when the Cr content increases. The B2 + L12 + BCC changes into B2 + FCC + BCC three-phase equilibria from 850 to 1150 °C, as the L12 phase region becomes narrow with rising temperature. The two-phase equilibrium, B2 + BCC, was found at all the isothermal sections investigated. Other three-phase equilibria were also discovered: B2 + α-Cr3Ga + BCC and Ni2Ga3 + α-Cr3Ga + L at 850 °C, and B2 + α-Cr3Ga + L at 1000 °C. Significantly, an athermal ω intermetallic compound with the space group of P (Formula presented.) m1 was observed distributing at the B2 phase in the quenched Ni45.98-Ga25.50-Cr28.52, Ni42.23-Ga15.70-Cr42.07 and Ni16.54-Ga13.63-Cr69.83 (at. %) alloys after being annealed at 1150 °C for 10 days. The high-resolution transmission electron microscopy (HRTEM) results reveal that the ω shows a crystallographic orientation of (Formula presented.) ; (Formula presented.) with the B2 parent phase.

Original languageEnglish
Article number7617
Issue number21
Publication statusPublished - 2022 Nov
Externally publishedYes


  • omega phase
  • phase diagram
  • shape memory alloys

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics


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