A powder-deposition apparatus for an additive manufacturing system includes a recoater, a mixer, and a powder feeder. The recoater is configured to discharge powder such that a powder layer is formed from the powder. The mixer is configured to mix a plurality of powder constituents to produce the powder and to dispense the powder to the recoater. The powder feeder is configured to selectively dispense a mass of each one of the plurality of powder constituents to the mixer such that a composition of the powder is selectively controlled.