Abstract:The influence of melt convection on dendrite growth during the upward-directional solidification of Pb-33%Sn binary alloys was investigated. The melt convection was modulated by traveling magnetic field. When the direction of traveling magnetic field was changed from upward to downward, the primary dendrite spacing gradually increased, and the distribution peak of the primary dendrite spacing shifted to the field of narrower spacing. These result from the different intensities of melt convection, which are controlled by the traveling magnetic field. The effects of the traveling magnetic field on melt convection are similar to those of adjustment in the gravity level, thus, the primary dendrite spacing varies. When the intensity of the traveling magnetic field was 1 mT, and the drawing speed was 50 μm/s, the gravity acceleration reached 0.22g for the downward-traveling magnetic field and 3.07g for the upward-traveling magnetic field.

Key words: directional solidification; microstructure; Pb-Sn alloy; traveling magnetic field