Columnar grains-covered small grains Cu–Sn alloy prepared by two-phase zone continuous casting

A new theory of two-phase zone continuous casting (TZCC) has been established in order to improve mechanical properties, corrosion resistance and conductivity properties of metals with wide solid–liquid two-phase zone. A Cu–Sn alloy with continuous columnar grains-covered non-columnar small grains of same phase microstructure containing many self-closed grain boundaries were produced by the self-developed TZCC process. Compared with water-cooled mold continuous casting Cu–Sn alloy, the tensile strength and ductility of the TZCC alloy are greatly improved, the corrosion resistance is improved up to fifteenfold, and the conductivity is improved by 12.2%. The excellent high strength may be due to the effective blockage of dislocation motion by numerous self-closed grain boundaries, which suppress the propagation of grain boundary corrosion, and the extremely low electrical resistivity and high ductility may be attributed to continuous columnar grains.