Experimental research on solidification structure of alloy 800H by linear electromagnetic stirring

Abstract

The solidification structures of alloy 800H fabricated with and without linear electromagnetic stirring (L-EMS) were investigated. The results show that the solidification structure of the alloy can be obviously affected by the forced convection in melt caused by L-EMS. The average size of equiaxed grains of the alloy with L-EMS decreases from 3.5 mm to 2.3 mm, and the ratio of equiaxed grain increases from 5% to 43% compared with that without L-EMS. The microstructure of the alloy without L-EMS is composed of fine equiaxed dendrites in the outermost layer and columnar dendrites in other areas, whereas that with L-EMS contains equiaxed dendrites, columnar dendrites and cross dendrites. In addition, the mechanism of dendrite fragment drift was proved by examining the composition change of the main alloying elements in the dendrite trunks at different solidification stage using an electron probe micro-analyzer (EPMA).

Keywords

• linear electromagnetic stirring; superalloy; dendrite fragment; solidification