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Systems of alloys for liquid phase alloying during sintering were investigated. The solidification range of alloys of Mn-Ni-Cr-Mo-Fe and Mn-Cu-Ni was determined. Alloys with the lowest and narrowest melting range were prepared and atomized in nitrogen. Admixtures of master alloys to water-atomized, forging grade, pure iron powder were sintered at 1232°C (2250°F). After hot forging, these P/M steels exhibited hardenabilities which were 75%-90% of theoretical hardenability, as calculated from the factors for conventional steels. Alloying efficiency was further improved to 85%-100% of theoretical hardenability when additions of approximately 2% silicon and 1% rare earth misch-metal were made to the master alloys. The silicon and rare earth misch-metal additions were used to enhance diffusion and sintering.