Laser powder bed fusion fabrication of CrCoFeNiMn-XTiC high-entropy alloy: Molecular dynamics study on tensile behavior, mechanical properties, and microstructural evolution

This study utilized laser powder bed fusion (LPBF) technology to fabricate CrCoFeNiMn-XTiC (X = 0 wt%, 5 wt%, 10 wt%, 15 wt%) high-entropy alloys (HEAs) with excellent tensile properties and surface hardness. Molecular dynamic (MD) simulations were employed to investigate the strengthening mechanisms of CrCoFeNiMn-XTiC HEAs at the molecular scale. The influence of various TiC particle contents on the microstructure, mechanical properties, and phase composition of HEAs was examined. The results indicated that the distribution of TiC particles at grain boundaries and the clustering effects refined the grain structure, thereby increasing the intensity of face center cubic (FCC) diffraction peaks within the HEAs. Transmission electron microscopy revealed that solid-solution strengthening, due to sigma phase precipitation, along with synergistic strengthening from dislocations and twins in LPBF-fabricated HEAs, resulted in enhanced surface strength. Combining MD simulations with tensile experiments, it was found that TiC particles hindered dislocation slip, controlled dislocation nucleation, and promoted the aggregation of Shockley and Stair rod dislocations into dislocation networks. This mechanism facilitated the formation of HCP structures and enhanced the tensile performance of HEAs. Specifically, CrCoFeNiMn-10 %TiC HEA exhibited the highest yield strength and possessed a higher surface hardness (379.01 Hv0.03).