Stabilization of L1₂ structured Cr₃Cu precipitates in a Cu-4.06Cr-1.25Nb alloy with high high-temperature strength

Abstract

Stable L1₂ structured Cr₃Cu precipitates were determined in a Cu-4.06Cr-1.25Nb alloy rather than b.c.c. structured Cr precipitates by transmission electron microscope (TEM) and three-dimension atom probe tomography (3DAP) at 450 ^oC. The precipitation sequence of the studied alloy aged at 400 ^oC was supersaturated solid solution → f.c.c. Cr phase → Cr₃Cu phase (L1₂). Nb atoms would segregate in the interface between the Cu and Cr phase, reduce the Cu/Cr interfacial energy, affect the precipitation, growth, phase transformation, and coarsening of the precipitate. These Cr₃Cu precipitates significantly improved the high-temperature strength of the Cu-Cr-Nb alloy (223 ± 5 MPa at 500 ^oC).

GRAPHICAL ABSTRACT

IMPACT STATEMENT

TEM images and calculations revealed that Nb can stabilize metastable Cr₃Cu precipitates (L1₂) by reducing the Cu/Cr interfacial energy, and provide a higher high-temperature strengthening effect than b.c.c. Cr.

KEYWORDS:

• Copper alloys
• precipitation
• coarsening
• first-principles calculation

Acknowledgements

This work was supported by the National Natural Science Foundation of China (51901250), and the Key Technologies R&D Program of Yunnan Province (202102AB080019-1).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by National Natural Science Foundation of China: [Grant Number 51901250]; National MCF Energy R&D Program of China: [Grant Number 2018YFE0306103]; Key Technologies R&D Program of Yunnan Province: [Grant Number 202102AB080019-1].