Influence of Ag addition on the microstructure and properties of Cu-6.5Fe-0.2Cr alloy prepared by upward continuous casting

Highlights: • Ag refines Fe dendrites, precipitates Fe phase and recrystallized grains. • The addition of Ag increased the coordinated deformation ability of Cu/Fe and dislocation density of alloy. • Ag increases the precipitation strengthening effect of the alloy. • The addition of Ag increased the mechanical properties and electrical conductivity of alloy. • The Cu-Fe-Cr and Cu-Fe-Cr-Ag alloys were continuously and stably prepared by upward continuous casting. -- Abstract: Cu-6.5Fe-0.2Cr (CFC) and Cu-6.5Fe-0.2Cr-1Ag (CFCA) alloys were prepared by upward continuous casting to investigate the influence of Ag on the microstructure, mechanical properties and electrical properties of CFC alloy. The properties testing discovered that the mechanical properties and electrical conductivity of CFC alloy were improved by the addition of Ag. The peak strength of CFCA alloy (622 MPa) was 33 MPa higher than that of CFC alloy, and the peak conductivity (67.8% IACS) was increased by 5% IACS after aging. The microstructure observation showed that Cr element was mainly distributed in the primary Fe phase. The addition of Ag refined and promoted the precipitation of nano-scale Fe phase, and improved the coordinated deformation ability of Cu/Fe, resulting in excellent comprehensive performance of CFCA alloy. In addition, the effect of Ag on nano-scale Fe phase precipitation kinetics was explored by the modified Johnson–Mehl–Avrami–Kolmogorov (JMAK). The addition of Ag reduced the activation energy of the Fe phase and promoted the precipitation kinetics of the Fe phase. And the activation energy of CFC and CFCA alloys was 66.1 and 63 kJ/mol, respectively.