Softening Resistance, Dimensional Stability and Corrosion Behaviour of Alumina and Rice Husk Ash Reinforced Aluminium Matrix Composites Subjected to Thermal Cycling

The softening resistance, dimensional stability and corrosion behaviour of stir cast alumina and rice husk ash reinforced aluminium matrix composites subjected to thermal cycling has been investigated. Aluminium hybrid composites having 10 wt% reinforcement consisting of alumina (Al2O3) and rice husk ash (RHA) in weight ratios of 1:0, 3:1, 1:1, 1:3, and 0:1 respectively were produced. The composites were subjected to varying thermal cycles of 3, 6, 9 and 12 from room temperature to 200 oC repeatedly. Hardness, linear change in dimensions, microstructural examination and corrosion test were used to characterize the composites produced. From the results, no obvious change in the microstructure could be discerned with thermal cycling. There were only marginal changes in hardness with increase in thermal cycling also less than 2 % change in linear dimensions was observed with thermal cycling. The composites were also observed to be very resistant to corrosion in 3.5 % NaCl solution with no appreciable change in corrosion resistance noted with increase in thermal cycling. However, in 0.3M H2SO4 solution, the corrosion resistance increased with increase in RHA content and samples subjected to 9 and 12 thermal cycles exhibited a relatively higher susceptibility to corrosion.