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

IMPACT STATEMENT TEM images and calculations revealed that Nb can stabilize metastable Cr3Cu precipitates (L1(2)) by reducing the Cu/Cr interfacial energy, and provide a higher high-temperature strengthening effect than b.c.c. Cr. Stable L1(2) 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 C-o. The precipitation sequence of the studied alloy aged at 400 C-o was supersaturated solid solution -> f.c.c. Cr phase -> Cr3Cu phase (L1(2)). 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 C-o).

Automated summary

The study demonstrated that the addition of Nb can stabilize metastable Cr3Cu precipitates by reducing the interfacial energy between Cu and Cr, resulting in a higher high-temperature strengthening effect. The Cu-Cr-Nb alloy with stable L1(2) structured Cr3Cu precipitates showed significantly improved high-temperature strength compared to the b.c.c. structured Cr precipitates.