A method of casting an alloy, the method comprising: providing a mold having a molten quantity of the alloy within a cavity of the mold , at least a portion of the mold being located within a secondary heating zone of an apparatus , the secondary heating zone causing the molten quantity of the alloy located within the secondary heating zone to be at a secondary heating temperature that is below yet sufficiently close to the liquidus temperature of the alloy so that the molten quantity of the alloy located within the secondary heating zone contains a liquid phase and a minor amount of a solid phase; causing relative movement between the mold and the apparatus so that the mold is translated from the secondary heating zone through a primary heating zone of the apparatus , the primary heating zone heating the molten quantity of the alloy located within the primary heating zone to a primary heating temperature above the liquidus temperature of the alloy, melting the solid phase within the molten quantity of the alloy, and thereby causing the molten quantity of the alloy located within the primary heating zone to contain only liquid phase; causing relative movement between the mold and the apparatus so that the mold is translated from the primary heating zone through an insulation zone of the apparatus and into a cooling zone of the apparatus , the insulation zone creating a thermal gradient within the molten quantity of the alloy located within the insulation zone to cause unidirectional solidification of the molten quantity of the alloy entering the cooling zone ; and then cooling the mold to produce a unidirectionally-solidified casting and a columnar crystal structure therein. providing a mold having a molten quantity of the alloy within a cavity of the mold , at least a portion of the mold being located within a secondary heating zone of an apparatus , the secondary heating zone causing the molten quantity of the alloy located within the secondary heating zone to be at a secondary heating temperature that is below yet sufficiently close to the liquidus temperature of the alloy so that the molten quantity of the alloy located within the secondary heating zone contains a liquid phase and a minor amount of a solid phase; causing relative movement between the mold and the apparatus so that the mold is translated from the secondary heating zone through a primary heating zone of the apparatus , the primary heating zone heating the molten quantity of the alloy located within the primary heating zone to a primary heating temperature above the liquidus temperature of the alloy, melting the solid phase within the molten quantity of the alloy, and thereby causing the molten quantity of the alloy located within the primary heating zone to contain only liquid phase; causing relative movement between the mold and the apparatus so that the mold is translated from the primary heating zone through an insulation zone of the apparatus and into a cooling zone of the apparatus , the insulation zone creating a thermal gradient within the molten quantity of the alloy located within the insulation zone to cause unidirectional solidification of the molten quantity of the alloy entering the cooling zone ; and then cooling the mold to produce a unidirectionally-solidified casting and a columnar crystal structure therein. <EOS>