Dependence of mechanical and surface characteristics on twin boundaries of CoCrFeNiAl high-entropy alloy

Abstract

The mechanical and surface properties of non-equiatomic CoCrFeNiAl high-entropy alloy (HEA) in the scratching process are explored through molecular dynamics simulation in the current work. The result reveals that the loading force decreases with the reduction of the twin thickness because the presence of excessive twinning in the structure is obviously related to the material softening. The average coefficient of friction (COF) is not proportional to the increment of twin thickness, and the COF in the scratching of monocrystal HEA is greater than in the scratching of twinning-containing workpieces. The plastic deformation behavior shows that the development of shear strain and residual stress into the workpiece in-depth decreases with rising the twin boundary distance. In addition, the pile-up height is larger with the increment of twin thickness, showing the ease of material removal in the machining for the large twin boundary sample. The number of wear atoms of a monocrystal sample is significantly larger than that of the twinning-containing specimens. The microstructure evolution shows that the dislocation and the stacking fault grow along the {111} primary sliding system for the monocrystal specimen, while the defects develop along the twin boundary for twinning-containing specimens.