Enhanced Mechanical and Shape Memory Properties of Laser Direct Energy Deposited CoCrFeMn High Entropy Alloy by Carbon Addition

In this study, the feasibility of improving the mechanical and shape‐memory properties of a CoCrFeMn high‐entropy alloy through carbon addition is investigated. Co20Fe18Cr19Mn0.6C (wt%) alloy is fabricated using laser direct energy deposition, and its properties are compared with those of the carbon‐free alloy. The carbon‐added alloy exhibits zigzag‐shaped grains with a fully face‐centered cubic (FCC) structure, while the carbon‐free alloy mainly consists of the hexagonal close‐packed (HCP) phase. After heat treatment, Cr‐enriched M 7 C 3 carbides precipitates, thereby retaining the zigzag morphology. Stacking faults are observed near the carbides. Both as‐built and heat‐treated alloys showed a <110> texture along the building direction, which is favorable for the FCC to HCP martensitic transformation. The carbon‐added alloy demonstrates higher yield strength and ductility than the carbon‐free alloy in the as‐built condition, whereas heat treatment reduces the strength since precipitates facilitate martensitic transformation. The maximum recovery strain of the carbon‐containing alloy is ≈3.4%, approximately four to five times higher than that of the carbon‐free alloy. These improvements are thought to be attributed to matrix strengthening, carbide‐induced stacking faults, and the favorable crystallographic texture.