Effect of Cr Addition on the Milling Process and Properties of Nanostructured Cu Alloys Prepared by Mechanical Alloying

Although nanostructure offers several advantages in improving the performance for Cu alloys prepared by mechanical alloying, the excellent properties have not been obtained to date primarily due to a single strengthening method or the Fe contamination introduced by the stainless steel grinding tank and balls. Herein, we added Cr to regulate the milling process and control the content of Fe doped into the Cu matrix. And the effects of Cr on the morphology, crystallite size, lattice strain and properties of Cu were studied. The results showed that adding an appropriate amount of Cr could prevent more Fe from being doped into the alloy matrix. When the Cr content was lower than 0.2 wt.%, the work hardening could be accelerated, so that the Cu alloys had smaller crystallite size, greater internal strain and higher tensile strength. But with continuous increase in Cr content, the crystallite sizes of the alloys began to increase again. Nevertheless, the nanostructured Cu alloys with particle size less than 10 nm were still obtained. In conclusion, by appropriately adjusting the Cr content, we demonstrated an improvement in the properties of the Cu alloys. The optimum properties were achieved by Cu-0.2 wt.% Cr with tensile strength of 517 MPa, ductility of 7.28% and electrical conductivity of 73.37% IACS. And the study provided a new idea for overcoming the Fe contamination in the metal matrix, and further improving high-performance Cu alloys through the combination of fine-grain strengthening and alloy strengthening.