A research team led by Professor Hyoung Seop Kim of the Department of Materials Science and Engineering at Pohang University of Science and Technology (POSTECH) announced in October 2026 that it had developed an ultra-high-strength iron-based alloy using metal 3D printing. The work was published in the International Journal of Extreme Manufacturing. Experimental data show that the alloy has a yield strength of 1,484 MPa, a tensile strength of 1,750 MPa, and a uniform elongation of 10%, giving it a strength-ductility combination superior to existing 3D-printed ultra-high-strength iron-based alloys such as 18Ni maraging steel and AerMet100. The team prepared maraging medium-entropy alloy powder with a composite ratio of iron (Fe), cobalt (Co), nickel (Ni), and molybdenum (Mo), and obtained an alloy material with almost no porosity through 3D printing. During forming, molybdenum enriches at the grain boundaries of hundreds-of-nanometer-scale honeycomb cellular structures. The team then used heat treatment to control the microstructure, greatly reducing brittle structures and achieving a uniform, dispersed distribution of highly ductile grains. The research was supported by the National Research Foundation of Korea's Nano and Material Technology Development Program and Leading Research Center Program, and in situ tensile tests were carried out using the J-PARC neutron accelerator facility in Japan. This route turns the cellular structures formed by rapid melting and solidification in 3D printing from a process by-product into a material design element, providing a reproducible process window for resolving the strength-ductility trade-off in ultra-high-strength iron-based alloys. For the metal powder and additive manufacturing supply chain, this means that composition control and batch consistency of Fe-Co-Ni-Mo medium-entropy alloy powder will become key variables in forming quality, and powder suppliers must match heat treatment process parameters to achieve the specified performance. Value for powder buyers: (1) Pay attention to the molybdenum ratio and oxygen content control of Fe-Co-Ni-Mo medium-entropy alloy powder, as these are the basis for the enrichment behavior at cellular structure grain boundaries; (2) require suppliers to provide forming performance data matched to high-temperature heat treatment processes, rather than relying only on powder particle size indicators; (3) include this type of alloy in the evaluation list of alternative materials for aerospace and defense structural components, and secure supply channels with medium-entropy alloy powder preparation capabilities in advance.