Solidification of Pb-Al Alloys Under the Influence of Electric Current Pulses

Continuous solidification experiments are carried out with Pb-Al alloys under the influence of the electric current pulses (ECPs). The results demonstrate that the ECPs mainly affect the microstructure formation through changing the energy barrier for the nucleation of the minority phase droplets (MPDs) and minority phase particles (MPPs) during cooling Pb-Al alloys in the liquid-liquid and liquid-solid phase transformation temperature ranges in advance of the solidification of the matrix liquid. For Pb-Al alloys with Al-rich droplets/particles as the minority phase, the ECPs lower the energy barriers for the nucleation of the MPDs/MPPs and cause a significant increase in the nucleation rate of the MPDs/MPPs and, thus, promote the formation of Pb-Al alloys with a well-dispersed or even nanoparticles dispersed microstructure. The ECPs parameters show an important influence on the microstructure formation of Pb-Al alloys. The refinement extent of the MPDs/MPPs increases with the increase in the peak current density. For a given peak current density, the refinement extent of the MPDs/MPPs increases with the increases in the pulse frequency and pulse width first, and then level off and become asymptotic.