激光定向能量沉积 18Mn 钢宽范围强韧性调控

To promote the application of laser directed energy deposition (LDED), as one of additive manufacturing technology, for low-alloy high-strength steels, it is crucial to clarify the impact of additive process parameters and subsequent heat treatment strategies on the microstructure and properties of the formed specimens. Low-alloy high-strength steel 18Mn was fabricated using LDED technology with different laser power inputs, followed by high-temperature normalizing heat treatment. The microstructural evolution and the mechanical property regulation methods of 18Mn steel are systematically investigated. The results demonstrate that with an increase in laser power, the microstructure of the 18Mn additive-formed specimens transitions from lath bainite to pearlitic-ferritic, with the corresponding mechanical properties shifting from high strength and low ductility to low strength and high ductility. After high-temperature normalizing heat treatment, the overall microstructure of the specimens becomes uniform and homogeneous, with improved ductility, and the microstructure and properties of specimens fabricated with different laser power inputs are similar. By varying the processing parameters and heat treatment conditions, the mechanical properties of 18Mn additive-formed parts can be controlled in a wide range, with yield strengths ranging from 355 MPa to 800 MPa and elongation from 10% to 27%. These findings provide important theoretical foundations and experimental data for the application of LDED technology in the additive manufacturing and remanufacturing repair of low-alloy high-strength steels.