Microstructure and corrosion behavior of Al3Ti/ADC12 composite modified with Sr

摘要

In this study, we investigated the effect of the addition of Sr (0wt%, 0.1wt%, 0.2wt%, and 0.3wt%) on the microstructure and corrosion behavior of Al3Ti/ADC12 composite by optical microscopy, X-ray diffraction, scanning electron microscopy, and energy diffraction spectroscopy. The results reveal that the alpha-Al phases were nearly spherical and 40 mu m in size and that the eutectic Si phases became round in the composite when the Sr content reached 0.2wt%. The Al3Ti particles were distributed uniformly at the grain boundary. The results of the corrosion examination reveal that the Al3Ti/ADC12 composite exhibited a minimum corrosion rate of 0.081 g center dot m(-2)center dot h(-1) for an Sr content of 0.2wt%, which is two thirds of that of unmodified composite (0.134 g center dot m(-2)center dot h(-1)). This improved corrosion resistance was due to galvanic corrosion, which resulted from the low area ratio of the cathode to anode regions. This caused a low-density corrosion current in the composite, thereby yielding optimum corrosion resistance.