Experimental investigations on the corrosion behavior of Al–Mg/B4C composites synthesized via powder metallurgy

Abstract

The goal of this project was to investigate the microstructure, hardness as well as corrosion behavior of Al - 4% Mg metal matrix composites containing boron carbide (B₄C) particles at different weight fractions (3, 6, and 9 wt.%). Composites were produced through powder metallurgy by compacting, sintering and characterizing using scanning electron microscopy (SEM), X-ray diffraction (XRD), hardness testing along with potentiodynamic polarization testing in 3.5% sodium chloride solution. The findings demonstrated that when sintered at 560 degrees Celsius (°C), particles of boron carbide dispersed evenly inside the Al-Mg matrix with low levels of porosity. Increasing the B₄C content improved hardness up to an optimal fraction of 6 wt.%; however, particle agglomeration at higher weight fractions reduced strengthening efficiency. Potentiodynamic polarization tests indicated that corrosion resistance was greater due to boron carbide particles up to a level of 6 % by weight as evidenced via lower corrosion current densities and reduced tendency to pitting, which was attributed to the barrier effect from ceramic reinforcement. At 9% by weight boron carbide, increasing agglomeration, microstructural defects and susceptibility to localized corrosion resulted from addition of boron carbide. The findings indicate that an optimum amount of boron carbide is necessary to optimize mechanical strength while providing the adequate levels of corrosion resistance; therefore, suggesting that the Al–4Mg–6B₄C composite is well-suited for marine and aerospace applications.