Effect of small amount of Mo addition on microstructure and mechanical properties of Fe-0.5Mn-0.5C sintered steels

Powder metallurgy Fe-0.5Mn-xMo-0.5C (x=0, 0.25, 0.4, 0.5) alloys were prepared by sintering the compact at 1 150 in H2 for 1 h. The effect of Mo addition on microstructure and mechanical properties of Fe-0.5Mn-0.5C sintered steels were analyzed by optical microscope, scanning electron microscope and mechanical properties testing. The results show that small amount of Mo addition (mass fraction ≤ 0.5%) can improve the sintered density, tensile strength, hardness and elongation of sintered parts simultaneously. When Mo content is 0.5%, the sintered density, tensile strength, hardness and elongation of the sintered parts reach maximum value of 7.10 g/cm3, 426 MPa, 92.2 HRB and 7.58%, respectively. These results come from the facts that Mo can promote the densification of Fe-0.5Mn-0.5C compacts. With Mo content increasing, the amounts of pearlites increase with narrower lamella space; the fraction of cleavage facets decreases and the number of dimples on the fractures of samples increases.