Effect of Lanthanum on Microstructure，Properties and Hot Workability of As-cast Cu-2.35Ni-0.59Si Alloy

As the third generation of lead frame material，Cu-Ni-Si based alloys are widely used in the field of integrated circuits. The rare earth element La，as a light rare earth element with large reserves，is commonly used as an impurity remover in alloy preparation，but the research and report on its use as a microalloying element is still in the exploratory stage. Therefore，in this study，the addition of La as a microalloying element for Cu-2.35Ni-0.59Si-0.11Mg-0.069Zn alloy was selected，and it is of important research value to explore the effects of La on the microstructure and properties of the as-cast alloy and the differences in thermal processing properties. Thermal deformation flow stress is an intrinsic property of materials exhibited by alloys at high temperatures，and it is of great significance in the subsequent development of reasonable hot working processes and parameters，as well as in the theoretical study of metal plastic deformation. This experiment used a Gleeble-3800D thermal simulation experimental machine to conduct thermal compression simulation experiments on Cu-Ni-Si and Cu-Ni-Si-La alloys，explored the thermal deformation behavior and thermal processing characteristics of the alloys，and solved and drew alloy constitutive equations and thermal processing diagrams. Microscopic characterization methods such as OM，SEM，and conventional performance testing methods were used to conduct a comprehensive study of the as-cast alloy. The results show that the addition of La can refine the grain size of the as-cast alloy but reduce the elongation of the as-cast alloy. The distribution of La-rich phase on the grain boundary causes the grain boundary to bend. The relationship between the flow stress，deformation temperature，and strain rate of the two alloys is the most consistent with the hyperbolic sinusoidal constitutive relationship. The final calculation results show that the thermal deformation activation energies of the two alloys are 785.6 and 858. 2 kJ∙mol-1，respectively；The reason for the difference between the thermal activation energy and the thermal working diagram of the alloy is due to the blocking effect of the La-rich particles formed by the addition of La on grain boundary motion and dislocation motion. © 2024 Editorial Office of Chinese Rare Earths. All rights reserved.