Ductile Fe-based BMGs with high glass forming ability and high strength

Fe-based bulk metallic glasses (BMGs) with high glass forming ability (GFA) and excellent mechanical properties were synthesized in Fe-Ni-Mo-P-C-B alloy system by copper mold casting. Results show that the glass forming ability of Fe74-xNixMo6P10C7.5B2.5 alloys increases first and then decreases as Ni content, x, increases from 0 to 11.1 at%, with its climax being reached at x is between 3.7 and 5.0. Analyses indicate that either Delta T-x and Delta H-endo or T-rg and gamma can not illustrate the GFA of obtained alloys solely. With increasing Ni element in Fe74-xNixMo6P10C7.5B2.5 alloys, the yield strength and Vicker's mircrohardness decline, while the plasticity increases, which implies that enhancing plasticity by adjusting the composition of alloys is followed with the loss of some strength. Serrated flow characteristics on the compressive stress-strain curves is observed for Fe74-xNixMo6P10C7.5B2.5 as x = 11.1 at%, which is considered to relate to its lowest glass transition temperature. These mechanical properties of BMGs are illustrated with bonding nature between the constituent elements.