Microsegregation and Solidification Shrinkage of Copper‐Lead Base Alloys

Abstract

Microsegregation and solidification shrinkage were studied on copper-lead base alloys. A series of solidification experiments was performed, using differential thermal analysis (DTA) to evaluate the solidification process. The chemical compositions of the different phases were measured via energy dispersive X-ray spectroscopy (EDS) for the Cu-Sn-Pb and the Cu-Sn-Zn-Pb systems. The results were compared with the calculated data according to Scheil's equation. The volume change during solidification was measured for the Cu-Pb and the Cu-Sn-Pb systems using a dilatometer that was developed to investigate the melting and solidification processes. A shrinkage model was used to explain the volume change during solidification. The theoretical model agreed reasonably well with the experimental results. The deviation appears to depend on the formation of lattice defects during the solidification process and consequently on the condensation of those defects at the end of the solidification process. The formation of lattice defects was supported by quenching experiments, giving a larger fraction of solid than expected from the equilibrium calculation.

Kinetic Simulations of Diffusion-Controlled Phase Transformations in Cu-Based Alloys

“…Moreover, the simulated content of Sn in the liquid phase is larger than that of in the solid phase in both the Cu-Pb-Sn and Cu-Pb-Sn-Zn alloys, while the content of Zn shows an opposite trend. These simulated results have been confirmed by the experiments [76]. Besides, the length of the region on the left side of solid/liquid interface in Fig.…”

“…It means that the addition of Zn will incerease the partitioning of Sn to the dendrite during the solidification. The predicted microsegregation behaviors in the Cu-Pb-Sn and Cu-Pb-Sn-Zn alloys have been verified by the reported experimental measurements [76]. Simulation of Precipitation.…”

“…For the simulation, the initial liquid composition is assumed to be homogeneous and equal to the nominal alloy composition; the starting temperature for the solidification process is selected to be 20 o C higher than the equilibrium melting temperatures, i.e. [76]. The simulation results show an excellent agreement with the measurements.…”

“…(a) (b) Figure 8 Calculated composition profile through half dendrite cross section in (a) Cu-4.7wt.%Pb-5.2wt.%Sn alloy, and (b) Cu-4.9wt.%Pb-5.2wt.%Sn-4.5wt.%Zn alloy during the solidification process along with experiemtnal data [76]. The cooling rate is 0.16 o C/s.…”

Effects of work-hardening and post thermal-treatment on tensile behaviour of solder-affected copper

“…Moreover, Pb does not have any tendency to form intermetallic compounds with Cu. [37][38][39][40][41] In addition, Pb does not affect the grain structure of Cu because it is practically insoluble in solid Cu. As a result, the tensile strength of material-III is the lowest and that of material-IV remains in between material-I and material-II at their as-cast condition.…”