Design of multicomponent master alloys for partial liquid phase sintering

Ferroalloys are widely employed in PM. For a particular ferroalloy, one can calculate its solidus and liquidus temperatures and decide whether it will remain either solid, fully or partially fused at sintering temperature. This approach is questionable; since many ferroalloys are fabricated via solidification, their states are non-equilibrium and there are regions containing phases precipitating in the beginning of freezing which have higher melting temperatures than regions with phases forming later on. During heating, Scheil’s solidification path backtracks and a fraction of liquid in the ferroalloy can be estimated at sintering temperature. If the fraction is significant, the utilization of this ferroalloy implies liquid phase sintering. Through computational thermodynamics, ferroalloys with promising compositions were discovered in Fe-C-Cr-Mn, Fe-C-Cr-Mn-Ni, Fe-C-Mn-Mo, Fe-C-Mn-Mo-Ni and Fe-C-Cr-Mn-Mo systems. That of the Fe-C-Cr-Mn-Mo system was fabricated and tried in practice. Compositional maps and mechanical properties of PM steels made with variations of this specially tailored ferroalloy are compared with those for which traditional ferroalloys were used.