COCRWNI ALLOY DESIGN FOR BIOMEDIC APPLICATIONS USING THERMODYNAMIC AND FIRST PRINCIPLE CALCULATIONS

• Main Author: Tamimi Prasetya Aji, Syamsul
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/65427
• Institution: Institut Teknologi Bandung

Industrial development and research on medical devices is one of the priority national development programs to overcome dependence on imported medical devices. One of the metal alloys that has the potential to be developed as a medical device is CoCrWNi. One of the medical devices that uses CoCrWNi alloy is a cardiac stent, an alloying element is needed to improve its shapeability. Selection of alloying elements is required to produce a good combination of mechanical properties, corrosion resistance, and biocompatibility of CoCrWNi alloys. With the development of metal alloy designs through computational methods, various alloying elements can be modeled easily so as to produce the desired mechanical properties in a short time and at lower costs. In this study, the design of the CoCrWNi alloy was modeled through thermodynamic calculations and the first principle with variations in the addition of alloying elements in the form of Cu, Mn, or Fe to obtain the value of Stacking Fault Energy (SFE) and the desired mechanical properties. A series of simulations for calculating the SFE of CoCrWNi alloys have been carried out to study the effect of temperature and concentration of alloying elements on the SFE value of CoCrWNi alloys. Calculation of the effect of temperature on the value of SFE is carried out through simulation of thermodynamic calculations in the temperature range of 0-1500 oC. Meanwhile, the effect of the alloying element concentration on the SFE value was simulated through thermodynamic and the first principle calculation at the alloying element concentration 4.5; 9; and 13.5 at.%. In the first principle method, calculations are also carried out to determine the equilibrium lattice parameters of the CoCrWNi alloy. The effect of alloying element concentration and supercell structure on the electronic structure of the CoCrWNi alloy was simulated at a temperature of 0 K using the first principle method. The value of the CoCrWNi alloy equilibrium lattice parameter from the first principle simulation (3.47 Å) is almost the same as the reference CoCrWNi alloy lattice parameter (3.473 Å). The SFE value of CoCrWNi alloy increases with increasing temperature and concentration of Cu, Mn, and Fe alloying elements both by thermodynamic and first principle calculation. The difference between the SFE values from the thermodynamic calculation and the first principle is quite low (12-54 mJ/m2). The difference in the results between the thermodynamic and first principle calculations is due to the difference in the location of the atoms modeled in the two methods. The addition of alloying elements will decrease the area of charge accumulation and the total DOS (Density of State) thereby increasing atomic bonding and SFE values. The combination of the addition of Cu and Mn gave an increase in the SFE value of the CoCrWNi alloy which was higher when compared to Cu or Mn alone at the same concentration.