Effect of SiCp multimodal distribution on pitting behavior of Al/SiCp composites prepared by reactive infiltration

The effect of coated-SiCp multimodal-size-distribution on the pitting behavior of Al/SiCp composites was investigated. α-SiC powders (10, 54, 86, and 146 μm) were properly mixed and coated with silica to produce porous preforms with 0.6 volume fraction of the reinforcement with monomodal, bimodal, trimodal, and cuatrimodal size distribution. The preforms were infiltrated with the alloy Al–13 Mg–1.8Si (wt.%) in argon followed by nitrogen at 1100 ºC for 60 min. The composites were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) before and after cyclic polarization measurements in 0.1 M NaCl de-aerated solutions. Results show that whereas corrosion and passivation potentials are not influenced with increase in SiCp particle size distribution, favorably, the susceptibility to pitting corrosion decreases. This beneficial effect is ascribed to the smaller area of the alloy matrix exposed to the chloride solution with augment in particle size distribution, substantially when going from monomodal to bimodal SiCp particle size distribution.

The multimodal-size-distribution of SiCp affects the pitting behavior of Al/SiCp composites prepared by the reactive infiltration of SiCp porous preforms with 0.6 volume fraction of the reinforcement with monomodal, bimodal, trimodal, and cuatrimodal size distributions. The susceptibility to pitting corrosion decreases with increase in particle size distribution. The photomicrograph shows typical microstructure conditions before and after cyclic polarization tests.Figure optionsDownload as PowerPoint slide