Effect of Cr element on tensile mechanical properties of Al0.3CoCrxFeNi high entropy alloys by MD simulations

High entropy alloys (HEAs) are multi-component metallic materials renowned for their exceptional thermal stability, superior corrosion resistance, and other outstanding properties, which make them highly promising for various applications. This study investigates the tensile mechanical characteristics of the Al0.3CoCrxFeNi high entropy alloys with varying chromium (Cr) contents (at%) through Molecular Dynamics simulations (MD). The results indicate that the tensile strength and elongation exhibit similar fluctuations. The mechanism of plastic deformation in the alloy transitions from a combined process involving both dislocation slip and twin deformation to one that is primarily characterized by single twin deformation. This change can be attributed to the lattice distortion induced by the incorporation of Cr into the alloy. Furthermore, a thorough investigation was conducted to assess the influence of temperature and strain rates on the mechanical properties of these alloys. Temperature fluctuations significantly affect the mechanical characteristics of the Al0.3CoCrxFeNi high-entropy alloys. As the temperature increases, the Young's modulus, tensile strength, and toughness decrease. Under the conditions of low strain rates and gradually rising temperature, the tensile strength, Young's modulus, and elongation of the Al0.3CoCr1.0FeNi HEAs decreased by 4.55 GPa, 12.91 GPa, and 2.9%, respectively. The plastic deformation mechanism gradually shifts from predominantly twin deformation to the coexistence of twin and dislocation slip. The tensile strength and elongation rise with an increase in strain rate. This phenomenon is attributed to the high stress levels at elevated strain rates, which activate multiple dislocation sources simultaneously, thereby increasing the number of dislocations and their interactions, leading to enhanced strength.