Improving mechanical properties and machining surface quality in a Fe49Mn30Co10Cr10N1 high-entropy alloy sheet by laser-assisted grinding

Laser-assisted grinding (LAG) was performed on the Fe 49 Mn 30 Co 10 Cr 10 N 1 (at.%) high-entropy alloy (HEA) cold-rolled sheet with the face-centered cubic (fcc) structure. A gradient microstructure along the thickness direction of the sheet was constructed, consisting of a work hardening layer on the grinding surface, a recrystallized (RX) layer in the grinding subsurface, a partially-recrystallized (PRX) layer in the transition region from surface to the core and a non-recrystallized (NRX) layer in the core. The studied HEA displays gradient characteristics in grain size, recrystallization fraction, dislocation density and the density of lath structures with local chemical order domains (LCO-laths). It achieves excellent comprehensive mechanical properties with yield and ultimate tensile strengths of 775 MPa and 945 MPa, uniform and fracture elongations of 38 % and 70 %, respectively. The results indicate that the yield strength of the studied HEA is approximately 2.2 times that of its homogeneous counterpart. This enhancement is attributed to various strengthening mechanisms , including grain refinement in the RX and PRX layers, the presence of dense LCO-laths and dislocations in the PRX and NRX layers, the work hardening layer introduced by grinding and hetero-deformation induced (HDI) strengthening. The satisfactory ductility and work hardening ability are mainly attributed to the HDI hardening, remarkable twinning and dislocation slip. In addition, the studied HEA achieves excellent machining surface quality, including a surface hardness of 2.9 GPa, a surface roughness R a of 0.55 μm, an average friction coefficient of 0.48 and a wear mass loss of 0.03 mg. These characteristics are attributed to the formation of a work hardening layer on the surface of the workpiece during grinding. The design strategy of constructing a gradient structure through LAG in this study can simultaneously enhance the comprehensive mechanical properties and machining surface quality of fcc HEAs, providing new insights for the effective production of high-performance metal sheets.