In this study, the combined effects of alloy compositions and porosity in powder metallurgy (P/M) steels on the phase transformation and mechanical properties were investigated. First, carbon steels and Astaloy CrM (Fe-3.0 wt.% Cr-0.5 wt.% Mo) steels with various porosities were produced using powder metallurgy routes, and their microstructure and mechanical properties were examined. Then, the phase transformation and resulting mechanical properties of porosity-free samples were simulated using the commercial software JMatPro (R) to examine the sole effect of alloy composition. By combining the porosity effect fitting models with the JMatPro results, we attempted to formulate a mathematical material model that describes the mechanical behaviors of the P/M steels. (C) 2015 Elsevier B.V. All rights reserved.