A Comparative Nanoindentation Study on HEA Coated FCC Metals and Stacking Fault Tetrahedra Evolution in HEA Coated Single Crystal Al: A MD Simulation Study

In the present study, the nanoindentation test has done on Mo20W20Co20Ta20Zr20 (HEA) film-coated single crystal (SC) Cu and Al by replacing the substrate SC Ni in the earlier reported study to compare the underlying deformation activities and mechanical properties using molecular dynamics (MD) simulation. The development mechanism of stacking fault tetrahedra (SFT) in Mo20W20Co20Ta20Zr20 coated SC Al has also been investigated. The comparative study suggests the appearance of different dislocation structures at higher indentation depth are effectively influence the plastic deformation in HEA-SC FCC specimens. The deformed structures seen in HEA-SC Ni are prismatic loops and interface distorted dislocations. The deformed structures seen in HEA-SC Cu are long lengthed Hirth partials, Lomer-Cottrell (LC) barriers, closed stair-rod partial dislocation steps, multi-dislocation loops, and complex distorted interface structures. The deformed structures seen in HEA-SC Al are SFT, LC barriers, closed stair-rod partial dislocation steps and loops. The SFT development in Mo20W20Co20Ta20Zr20 coated SC Al is dislocation-based mechanism. The dislocation-based mechanism is primarily governed by stacking fault (SF) planes’ interaction and dislocation gliding. The shear strain and displacement vector plots confirm the growth of distorted dislocation structure below the indenter tip in HEA coated SC Ni is relatively more symmetric and significant than others due to its high stiffness. In HEA coated SC Cu; the appearance of complex distorted dislocation structures at the interface restricts the plastic deformation to a greater extent in the interface layer.