Electrical and Corrosion Behaviour of Aluminium-Aluminium Nitride Particulate Composite produced via Powder Metallurgy

Abstract

The properties of aluminium nitride (AlN) such as good coefficient of thermal expansion, good wear and corrosion resistance, high mechanical strength, good resistance to thermal shock and good electrical properties have continued to attract research attention in recent times. In this paper, the interest is to investigate the influence of AlN on the electrical conductivity and corrosion properties of Al-AlN particulate composite produced using powder metallurgy. The samples were compacted using the pressure of 450MPa and sintered at 550 oC for 30 minutes using the two-step sintering method. Fourpoint probes machine was used to determine the electrical resistivity and subsequently the electrical conductivity of the samples. The samples were immersed in 0.05M NaOH for 24 hours to determine their corrosion behaviour using the weight loss method. The corroded samples were characterized using X-ray Diffractometer (XRD) and Scanning Electron Microscope (SEM). The result of the electrical conductivity of the samples increased with both the amount of reinforcement and magnesium added. The unreinforced aluminium sample recorded the lowest value of electrical conductivity while the sample with composition Al-16.25wt%AlN-1.0wt%Mg gave the highest value, 131.33 (Ωm)-1. The results of XRD analyses revealed peaks of aluminium hydroxide (Al(OH)3) as the main corrosion product on the samples. The results show that corrosion rates of the samples decrease with weight fractions of AlN and Mg. The sample containing Al-16.25wt%AlN-1.0wt%Mg offered the best corrosion resistance with a corrosion rate equivalent to 22.74mm/y; while the unreinforced aluminium sample corroded the most, 37.19mm/y.