A method for manufacturing a metallic article comprising the steps of: providing or obtaining a metallic material in powder form; using an additive manufacturing process, building the metallic article from the powder-form metallic material, layer-by-layer, in a build direction, wherein as a result of the additive manufacturing process, the metallic article comprises columnar grain structures oriented in the build direction; building a sacrificial piece onto the metallic article using the additive manufacturing process, the sacrificial piece being metallurgically coupled to the metallic article and comprising the metallic material; and conveying the metallic article through a gradient furnace in a direction of conveyance from a first area of the gradient furnace to a second area of the gradient furnace to increase a size of the columnar grain structures in the metallic article, wherein the metallic article is conveyed through the gradient furnace in an orientation such that the columnar structures oriented in the build direction are substantially parallel to the direction of conveyance, wherein the first area of the gradient furnace heats the metallic article to a temperature that is below a solvus temperature of the metallic material and the second area of the gradient furnace heats the metallic article to a temperature that is above the solvus temperature of the metallic material, the temperature of the gradient furnace increasing in a gradated manner from the first area to the second area, and wherein the metallic article is oriented with respect to the gradient furnace such that the sacrificial piece enters the gradient furnace subsequent to the metallic article onto which the sacrificial piece is built. providing or obtaining a metallic material in powder form; using an additive manufacturing process, building the metallic article from the powder-form metallic material, layer-by-layer, in a build direction, wherein as a result of the additive manufacturing process, the metallic article comprises columnar grain structures oriented in the build direction; building a sacrificial piece onto the metallic article using the additive manufacturing process, the sacrificial piece being metallurgically coupled to the metallic article and comprising the metallic material; and conveying the metallic article through a gradient furnace in a direction of conveyance from a first area of the gradient furnace to a second area of the gradient furnace to increase a size of the columnar grain structures in the metallic article, wherein the metallic article is conveyed through the gradient furnace in an orientation such that the columnar structures oriented in the build direction are substantially parallel to the direction of conveyance, wherein the first area of the gradient furnace heats the metallic article to a temperature that is below a solvus temperature of the metallic material and the second area of the gradient furnace heats the metallic article to a temperature that is above the solvus temperature of the metallic material, the temperature of the gradient furnace increasing in a gradated manner from the first area to the second area, and wherein the metallic article is oriented with respect to the gradient furnace such that the sacrificial piece enters the gradient furnace subsequent to the metallic article onto which the sacrificial piece is built.