Solidification microstructure characteristics of Cu–Pb alloy by ECP treatment

The effects of high-density electric current pulse (ECP) treatment on the solidification of Cu–37.4 wt% Pb monotectic alloy melt were investigated. Compared to the method of molten glass purification combined with cyclic superheating, ECP treatment created finer microstructures of Cu–Pb alloys, with more homogeneous distribution of the Pb phase in the matrix. This phenomenon can be explained by the cluster theory for liquid metals and the non-equilibrium diffusion theory. First, ECP treatment could cause the fission of larger atomic clusters to increase the undercooling that enabled a large number of smaller clusters to grow and reach the critical nucleation radius. Second, ECP treatment could reduce the diffusion energy barrier to enhance the non-equilibrium diffusion of solute atoms and suppress the segregation of Pb.

Effect of High Density Electric Current Pulse on Solidification of Cu-37.4 wt.%Pb Monotectic Alloy Melt

The effect of high-density electric current pulse (ECP) on the solidification of Cu-37.4 wt.%Pb monotectic alloy melt was investigated. The microstructure formation mechanisms of ECP were clarified according to liquid metal cluster theory. The results demonstrated that with ECP treatment, the microstructure of Cu-Pb monotectic alloy became finer, the distribution of Pb phase in the matrix was more even and the solute trapping was significantly apparent. Based on the metal liquid cluster theory under ECP, the solid solubility increase result might be due to the salvation clusters increase under the action of pulse current, leading to the binding force increase among solute atoms and solvent atoms. Simultaneously, the aforementioned results were verified through the Differential Scanning Calorimetry (DSC) curve analysis. The results of hardness test, anti-friction test and wear- resistance test show that the ECP can enhance the hardness, improve the properties of anti-friction and wear-resistance of the alloy.

Effect of the Third Element Ni on the Solidification Microstructure of Undercooled Cu-40 wt.% Pb Monotectic Alloy Melt

In this paper, the evolution of solidification microstructure of Cu-40 wt.% Pb monotectic alloy of the third element Ni pair under deep undercooling conditions was studied. By comparing the phenomena of liquid phase separation during deep undercooling and rapid solidification of Cu-40 wt.% Pb monotectic alloy, the melt of the alloy increases with the undercooling, and the solidification structure appears uneven or even stratified. With the addition of the third element Ni, the liquid phase separation can be effectively inhibited by the change of interfacial energy. The solidified structure undergoes the transformation from coarse dendrite to the first kind of granular and refined dendrite in a wide undercooling range. When the undercooling reaches 143 K, the structure begins to show an inhomogeneous trend.

MACHINABILITY ANALYSIS OF AN AL-1,2% Pb ALLOY SOLIDIFIED IN A HORIZONTAL DIRECTIONAL DEVICE

In general, the binary monotectic alloys are characterized by the limited solubility in the liquid state, which gives them a benefited tribological behavior such as wear resistance. Researches regarding the development of monotectic alloy microstructures during the unsteady-state heat flow conditions are fundamental, as it encompasses most of the solidification industrial processes. However, the microstructural relationship between the mechanical properties of monotectic alloys is little explored and practically nil. In this context, the present study consists of investigating and correlating solidification thermal variables and structural parameters such as microhardness and machinability (cutting temperatures and tool wear) of Al-1.2wt% Pb alloy, in a horizontal directional device. It was observed that the cutting temperature and tool wear results complement each other when correlated with position and interphase spacing, indicating that for smaller interphase spacings the addition of lead harms machinability.