In various embodiments, metallic alloy powders are utilized as feedstock, or to fabricate feedstock, utilized in additive manufacturing processes to form three-dimensional metallic parts. Such feedstock includes composite particles each comprising a mixture and/or alloy of a first constituent metal and one or more second constituent metals, where each of the particles comprises a plurality of grains each surrounded by a matrix, the grains comprising the first constituent metal, and the matrix comprising the one or more second constituent metals.