EFFECT OF NB OR ZR ADDITION AND SINTERING TEMPERATURE ON THE HARDNESS AND CORROSION RESISTANCE OF MG-5ZN ALLOY USING THE POWDER METALLURGY

• Main Author: Sriwijayanti, Ardilla
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/72218
• Institution: Institut Teknologi Bandung

Magnesium alloy, as an ultra-lightweight metallic structural material, has been increasingly used in the transportation industry to reduce the weight of vehicles. Vehicle light-weighting is today recognized as one of the predominant approaches to improve fuel efficiency and reduce environmental emissions. On the other hand, low strength and poor corrosion resistance limits the development of magnesium alloys. The Mg-Zn alloy exhibits one of the highest hardening responses of all the magnesium alloys. However, the use of Mg-Zn based alloys in automotive is not as high as other Mg alloys. Some elements that are prospective for further research due to their potential in improving Mg-Zn alloy properties are zirconium as a good grain refiner and niobium as reinforcing particles in a magnesium matrix. Accordingly, this research was focused on studying the effect of Zr and Nb and sintering temperature in Mg-Zn alloys on hardness, corrosion properties, and microstructure to improve Mg-Zn alloys performance. The research started with the preparation of Mg, Zn, Zr, and Nb powders. The process was continued by Planetary Ball Milling at a speed of 700 rpm for 2 hours, then compaction was carried out at a pressure of 100 kg/cm2. Sintering variations at temperatures of 400, 450, 500 and 550 °C were conducted for 2 hours. The sintered samples were cut into several pieces for hardness testing using the Vicker Hardness Test method and microstructure observations with the optical microscope and Scanning Electron Microscope-Energy Dispersive Spectroscope (SEM-EDS). Samples showing the maximum Vicker hardness value were tested for corrosion properties using potentiodynamic polarization and Electrochemical Impedance Spectroscopy (EIS) methods. The addition of 0.5 wt% Nb and 0.5 wt% Zr had an effect on increasing the hardness of the Mg-5Zn alloy. The highest hardness value of 85.57 HV was obtained in the Mg-5Zn-0.5Zr sample which was sintered at 450 °C. Meanwhile, the addition of 0.5 wt% Nb and 0.5 wt% Zr increased the corrosion resistance and decreased the corrosion rate of the Mg-5Zn alloy. Mg-5Zn alloy added with 0.5 wt% Nb gave the best corrosion resistance value and the lowest corrosion rate of 7.89 mm/year. Samples sintered at 450 °C gave more significant corrosion resistance than samples sintered at 400 °C.