A process for casting a turbine wheel includes steps of identifying a metal composition from which the turbine wheel is to be cast, providing a mold that defines a cavity into which molten metal composition is to be poured for casting the wheel, providing a seed member made of the metal composition and having an equiaxed grain structure, disposing at least a portion of the seed member within the cavity of the mold, pouring the molten metal composition into the cavity such that the molten metal composition envelops the portion of the seed member within the cavity, and controlling the process so that the portion of the seed member at least partially melts through contact with the molten metal composition and so that, upon cooling, the metal composition around the seed member solidifies with an equiaxed grain structure as precipitated by the equiaxed grain structure of the seed member.