Effect of Y and Mg on the Solidification Structure of Fe-36Ni Invar Alloy

摘要

The effect of Y and Mg on the solidification structure of Fe-36Ni invar alloy melted in a carbon tube furnace was investigated using digital camera, scanning electron microscopy (SEM) and energy dispersive spec-troscopy (EDS). The results showed that Y or Mg addition could remarkablly refine the solidification structure and increase the fraction of equiaxed grains. Great amount of high-melting point compounds (Y-2O-2S, MgS and MgS-MgO) formed in the alloy with the addition of Y and Mg respectively. Based on the theory of lattice misfit, the effectiveness of high-melting point compounds as heterogeneous nuclei of y-matrix was calculated. The calculation of the lattice misfit between Y_2O-2S, MgS and y-matrix, which were far less than 12, showed that Y_2O_2S and MgS acted as heterogeneous nuclei were highly effective. However, MgO could not serve as the heterogeneous nuclei because the lattice misfit between it and y-matrix exceeded 12.