Effects of Solute Elements on Primary and Secondary Dendrite Arm Spacings in Fe‐based Alloys

Abstract

There have been many experiments and theoretical studies of primary dendrites, and most of which have focused on the effects of extrinsic factors such as solidification rate and temperature gradient. However, intrinsic factors such as the kind of solute element and initial solute concentration are also considered to be important for controlling the spacing of primary dendrites.In this study, the effects of intrinsic factors on primary and secondary arm spacings of dendrites were investigated, and changes in a microsegregation index with changes in primary arm spacings and equilibrium distribution coefficient of each solute element were also examined. Fe‐Cr‐C, Fe‐C‐Cr, Fe‐C‐Cr‐Mo, Fe‐C‐Cr‐Mo‐V and Fe‐C‐Cr‐Mo‐V‐W alloys were solidified unidirectionally and water‐quenched. The primary arm spacing increased with increase in initial solute concentration in all alloys because the range of solidification temperature increased with increase in solute concentration. On the other hand, the secondary arm spacing in all alloys decreased with increase in initial solute concentration, and it was proportional to about the one‐third root of local solidification time. The microsegregation index increased with increasing primary arm spacing and with decreasing equilibrium distribution coefficient.