Effects of copper content on microstructure and mechanical properties of powder-forged rod Fe-C-Cu alloys manufactured at elevated temperature

The microstructure and mechanical properties of powder-forged Fe-C-Cu alloys manufactured at an elevated temperature were evaluated. It was found that the mechanical properties of the alloys were no worse than those in the literature, and the contribution of copper to the strength was quantified: the major strengthening mechanism of copper is grain-refinement strengthening rather than precipitation strengthening. Then, to ensure the safety of the elevated-temperature manufacturing, the hot-deformation behaviour of the Fe-C-2.5Cu alloy was investigated via construction of the constitutive equation and the hot-processing map, which proved that the high-temperature manufacturing was not only safe but also efficient. Finally, fatigue tests were conducted on the powder-forged connecting rods and 5154 wrought steel connecting rods for the same engine application, and the results showed that the powder-forged connecting rods had better fatigue strength and higher reliability.