Effect of Mn Content on Microstructure and Mechanical Properties of Fe-Mn-Cr-C High-Manganese Steels Produced Using Laser-Directed Energy Deposition

The microstructure and mechanical properties of high-manganese steel (HMnS) fabricated using laser-directed energy deposition (LDED) with Fe-Mn-4Cr-0.4C alloys with Mn contents of 13, 18.5, and 24 wt% are investigated. Additionally, the effect of annealing heat treatment on the microstructure and mechanical properties of the deposited HMnS is examined. Regardless of the manganese content, the deposited HMnS exhibits a fine microstructure without any defects (cracks or voids) and a strong fibrous texture along the < 001 >//building direction of the primary austenite phase. In addition, regardless of the manganese content, the grain size increases during annealing heat treatment, and the hardness decreases as the annealing temperature increases. The strength tends to decrease as the Mn content increases in the as-built state. In addition, regardless of the Mn content, the yield strength and ultimate tensile strength tend to decrease owing to the effect of annealing heat treatment. Although the maximum elongation of 18.5Mn and 24Mn does not change significantly upon heat treatment, the maximum elongation of 13Mn is greatly reduced by annealing. The deformation behavior of HMnS is characterized by transformation-induced plasticity (TRIP) for 13Mn and both TRIP and twinning-induced plasticity for 18.5Mn and 24Mn.