Hardness and tensile properties of Fe–P based alloys made through powder forging technique

High density Fe–P binary, Fe–P–Cr ternary as well as Fe–P–Cr–Si quaternary alloys were made using a hot powder forging technique. In this process mild steel encapsulated powders were hot forged into slabs, hot rolled and annealed to relieve the residual stresses. These alloys were characterized in terms of microstructure, porosity content/densification, hardness and tensile properties. Densification as high as 98.9% of theoretical density has been realized. Hot powder forging using channel die showed better densification than that obtained using flat die. Microstructures of these alloys consist of single-phase ferrite only. Rolled and annealed microstructure showed lesser porosity content than the forged and homogenized one. Phosphorous causes more hardening of ferrite than silicon in solid solution with iron. Alloys containing 0.35 wt%P, such as Fe–0.35P, Fe–0.35P–0.35Cr and Fe–0.35P–0.35Cr–1Si alloys showed very high ductility with low work hardening coefficient. As forged and hot rolled Fe–0.35P alloy showed very high elongation and it improved further on annealing. Alloys containing 0.7wt%P, such as Fe–0.7P, Fe–0.7P–0.7Cr and Fe–0.7P–0.7Cr–1Si alloys showed very high strength. However, they showed limited ductility with higher work hardening coefficient. It was observed in this present investigation that, the alloying addition, such as Si and Cr to Fe–P based alloys caused increase in strength associated with the reduction in ductility. Alloys developed in the present investigation were capable of hot/cold working to very thin gage of sheets and wires.