THE EFFECT OF CU ADDITION ON THE MECHANICAL PROPERTIES AND STACKING FAULT ENERGY OF HIGH ENTROPY ALLOY FENICOCR: A FIRST-PRINCIPLES STUDY

• Main Author: Immanuel Pane, Eri
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/85278
• Institution: Institut Teknologi Bandung

The demand for materials with excellent mechanical properties, formability and sustainability in manufacturing industries such as additive manufacturing continues to grow. FeNiCoCr is one type of high entropy alloys that has the potential to be developed in additive manufacturing. However, the price of cobalt (Co) powder significantly increases the cost of the raw material, so substitution with pure copper (Cu), which has a much more affordable price, is potentially an ideal alternative in the manufacturing process. Moreover, the addition of a certain amount of Cu to high entropy alloys has been tested to improve the mechanical and thermal properties of the alloys. Therefore, this study aims to investigate the effect of Cu addition on the lattice parameters, elastic properties, stacking fault energy (SFE) and electronic structure of FeNiCoCr. The calculations performed in this study were carried out using the CASTEP software by applying the method of first-principles: density functional theory. The calculations of lattice parameters, SFE, and electronic structure were carried out on the 24 atomic structure of the alloy with the addition of 4.17 and 8.33 at.% Cu. Meanwhile, the calculation of the elasticity constant was carried out on the 16-atom alloy structure with the addition of 6.25 and 12.5 at.% Cu. Lattice parameters were calculated by manual (electronic minimization) and automatic (ionic minimization) methods. SFE calculations were performed by calculating the total energy difference of the structures with and without stacking faults. Further investigations were carried out by analysing the density of states and charge density to determine the effect of Cu addition. Elasticity and hardness properties were calculated using the Voigt-Reuss-Hill approximation and Tian equation models. The lattice parameters of FeNiCoCr increased with the addition of Cu, from 3.51 to 3.515 Å at 4.17 at.% Cu and 3.518 Å at 8.33 at.% Cu. At the same time, the hardness and strength of the alloy increased, but then decreased with the addition of Cu. In contrast, the HEA decreased followed by an increase in ductility with the addition of Cu. The SFE of FeNiCoCr showed a consistent decrease with the addition of Cu, from 79.32 mJ/m2 to 54.92 mJ/m2 and 54.77 mJ/m2 respectively. The decreasing trend of the SFE is related to the decrease of the density of states around the Fermi level and the increase of the charge accumulation due to the substitution of Co by Cu, thus weakening the bonds between atoms and increasing the interlayer distance.