Embodiments of the invention relate to methods of forming polycrystalline diamond compacts (“PDCs”), wherein the PDC includes a polycrystalline diamond (“PCD”) table in which at least one Group VIII metal is at least partially alloyed with phosphorus and/or at least one other alloying element to improve the thermal stability of the PCD table. The disclosed PDCs may be used in a variety of applications, such as rotary drill bits, machining equipment, and other articles and apparatuses.