Erosion–corrosion characteristics of squeeze cast aluminium alloy/SiC composites in water and sodium chloride solutions containing sand

Abstract

The erosion–corrosion behaviour of a squeeze cast aluminium alloy (Al–Cu) dispersed with either 10 vol.-%SiC particles or SiC fibres was investigated in slurry environments of 3%NaCl (aqueous) + 40 wt-% sand and water + 40 wt-% sand over a range of test durations at a linear speed of 7·06 m s^-1. Test results indicated higher weight loss for the SiC composites than for the matrix alloy in 3%NaCl + 40 wt-% sand while the reverse trend was noted when the tests were conducted in water + 40 wt-% sand. Severe attack around the dispersoid/matrix and precipitate/matrix interfaces by the NaCl environment caused loosening of the dispersoid phase followed by the subsequent removal of the dispersoids. This resulted in a higher weight loss for composites than for the base alloy in NaCl containing sand. Corrosion processes appear to dominate in this case. The lower weight loss of the composites compared with the matrix alloy in water + 40% sand could be attributed to the protection provided by the SiC phase to the softer matrix. Erosion appears to be the predominant mechanism of material removal in this case. Furthermore, the SiC fibre composite suffered from more weight loss than that containing SiC particles in both the test environments. Results have been explained on the basis of analysis of eroded–corroded surfaces and subsurface regions.