Polycrystalline diamond compacts (“PDCs”) include a polycrystalline diamond (“PCD”) table in which cobalt is alloyed with phosphorous to improve the thermal stability of the PCD table. For example, a PDC includes a substrate and a PCD table including an upper surface spaced from an interfacial surface that is bonded to the substrate. The PCD table includes a plurality of diamond grains defining a plurality of interstitial regions. The PCD table further includes an alloy comprising at least one Group VIII metal and phosphorous. The alloy is disposed in at least a portion of the plurality of interstitial regions.