Microstructural stability and age-hardening behavior of Re-added dual two-phase Ni₃Al and Ni₃V intermetallic alloys

Abstract

The effect of Re addition on the microstructure and hardening behaviour of the dual two-phase Ni₃Al (L1₂) and Ni₃V (D0₂₂) intermetallic alloy was investigated by scanning electron microscopy, transmission electron microscopy and Vickers hardness test. The two-phase eutectoid microstructure accompanying the Re-rich precipitates were observed in the channel region of the alloys in which Re substituted for Ni but not in those in which Re substituted for Al and V. The concomitant addition of Nb (or Ta) with Re more stabilized the two-phase eutectoid microstructure and consequently more induced the fine precipitates in the channel region. The annealing at temperatures below the eutectoid temperature was necessary to induce the fine precipitates in the channel region and thereby result in the precipitation hardening. The fine precipitation in the channel region and related hardening was attributed to the alloying feature so that Re is soluble in the A1 (fcc) phase at high temperatures and becomes less soluble in the two intermetallic phases decomposed from the A1 phase at low temperatures.

Keywords:

• multiphase intermetallics
• precipitate-hardening
• microstructure
• transmission electron microscopy
• Ni₃Al
• Ni₃V

Acknowledgement

The authors are grateful to Mr. S. Ishii of formally undergraduate student at Osaka Prefecture University for his technical assistance.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported in part by a Grant-in-Aid for Scientific Research (B) [grant number 26289263] from the Japan Society for the Promotion of Science (JSPS).