HIGH ENTROPY ALLOY COCRNIFEAL AND COCRNIFESI DESIGN WITHTHERMODYNAMICS AND FIRST-PRINCIPLES CALCULATIONS

• Main Author: M.Murtadho
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/69384
• Institution: Institut Teknologi Bandung

In the Indonesian National Development Master Plan (RIPIN) compiled in 2015, one of the strategic industries planned to be developed for national development is the aerospace industry. Materials for aerospace components can be developed domestically, but aerospace materials must have certain criteria that must be achieved, namely toughness, resistance at high temperatures (creep), high fatigue strength, and oxidation resistance, but also have low density. High entropy alloys have the potential to be an aerospace material. The properties of high-entropy alloys are closely related to the deformation mechanism present in the alloy. The stacking fault energy of the alloy is indicated by the stacking fault energy (SFE) so that the properties of the high entropy alloy can be modified by adjusting the value of the SFE. A series of simulations for calculating the SFE of CoCrNiFeAl and CoCrNiFeSi alloys have been carried out to analyze the effect of the existing elemental composition and temperature on the SFE value of the alloy. Calculation of the effect of temperature on the value of SFE is carried out through simulation of thermodynamic calculations in the temperature range of 0-1127oC. To determine the effect of elemental composition, calculations were carried out using the thermodynamic method with variations of each element up to 35% and calculations using the first-principles method with element variations by replacing Al, Fe, and Si elements with Cr elements up to 13%. In the first-principles method, calculations were also carried out to determine the electronic structure of the CoCrNiFeAl and CoCrNiFeSi alloys. The results of the SFE in both methods are then compared with each other and associated with the mechanical properties that arise so that the alloy design can be analyzed so it can approach the properties of the aerospace material. The first-principles method is carried out at absolute zero temperature (0 K). In thermodynamic calculations, the SFE value of the CoCrNiFeAl alloy is 90.88 mJ/m2 and can be increased by the addition of Co, Ni, Fe, and Al elements as well as the reduction of Cr. Meanwhile, the SFE value of the CoCrNiFeSi alloy is 14.47 mJ/m2 and can be increased with the effect of adding Co, Ni, and Fe and reducing Cr and Si. The SFE value also increases as the temperature increases. In the first-principles calculation, the SFE value of the CoCrNiFeAl alloy is 143.20 mJ/m2 and the SFE value of CoCrFeNiSi is 85.91 mJ/m2. In CoCrNiFeAl alloy, the SFE value decreases with the addition of Cr and reduction of Fe and Al. In the CoCrNiFeSi alloy, the SFE value will be lower along with the addition of Cr and reduction of Fe and Si elements. The value of SFE can be analyzed from changes in the electronic structure of the CoCrNiFeAl and CoCrNiFeSi alloys through charge density analysis, as well as analysis with the density of states (DOS).