Grain refinement of copper by the addition of iron and by electromagnetic stirring

Abstract

The effect of iron additions in the range of 0.57 to 7.5 wt pet on the grain size of electromagnetically levitated copper-iron alloys was investigated. The samples were solidified while levitated or quenched in water from the molten state. The addition of iron was found to be effective in reducing the grain size of copper, and the average grain size decreased as the iron content was increased up to the peritectic liquid composition of about 2.8 wt pet Fe. Beyond this composition, the grain size of the samples solidified in the levitated state was insensitive to the iron content, whereas that of the quenched samples continuously decreased with increasing iron content. The results indicate that electromagnetic stirring causes fragmentation of copper dendrites in the hypoperitectic region, and hence enhances grain refinement. In the hyperperitectic region, on the other hand, the stirring has a detrimental effect on the grain refinement by agglomerating the primary iron particles which act as heterogeneous nucleation sites for the copper matrix.