Investigation into Plastic Deformation and Machining-Induced Subsurface Damage of High-Entropy Alloys

Abstract

High-entropy alloys (HEAs), which contain more than five principal elements with equal or near equal atomic percent, exhibit high wear resistant, high strength, and great plasticity. However, the plastic deformation mechanism and the machining-induced subsurface damage of HEAs at nanoscale are not yet fully understood, to limit their widely practical utility. Based on the experiment, AlCrFeCuNi HEA of atomic model is built through a melting and quick quenching method. In this work, we study the mechanical behaviors of AlCrFeCuNi HEA under uniaxial tensile loading and scratching processes by molecular dynamics (MD) simulations, in terms of the scratching force, atomic strain, atomic displacement, microstructural evolution, and dislocation density. The results show that the HEA obtained from MD simulations not only has high strength, but also exhibits good plasticity which is qualitatively consistent with the experiment. The dislocation gliding, dislocation pinning, and twinning subjected to the severe atomic lattice distortion and solid solution effects are still the main mechanism of plastic deformation in HEA. In addition, the larger tangential and normal forces and higher friction coefficient take place in HEA due to its outstanding strength and hardness, and high adhesion over the pure metal materials. Furthermore, the excellent comprehensive scratching properties of the bulk HEA are associated with the combined effects of multiple strengthening mechanisms, such as dislocation strengthening, deformation twinning strengthening as well as solute strengthening. This atomistic mechanism provides a fundamental understanding of plastic deformation and scratching behavior in HEA.