Impact of Transition-Metal Elements on Grain Refiner Performance in AA6061

Grain refinement during aluminum casting is beneficial for both Direct Chill (DC) casting of wrought alloys and shape casting of foundry alloys. The resulting equiaxed structure is essential for positive and predictable responses to post-casting treatments and final mechanical properties. In addition, the uniformity and refinement of the as-cast structure reduces hot-tearing susceptibility and thus leads to faster casting speeds. Recent developments on next-generation aluminum alloys incorporate transition metal elements to either enhance the amount of alpha iron-silicon intermetallics, or modify fracture behavior through the precipitation of dispersoids during homogenization. The purpose of this investigation was to determine if certain of these transition-metal elements impact the grain refining performance of TiB₂ in AA6061. Investigations were performed for Cr, V, and Zr as a function of time to determine if any substitutional reaction occurred during periods of time of interest to the casthouse.