Mechanical Behavior in the Silicon Carbide Reinforced Aluminum 6061 Composites Degraded by Room or High Temperature 3.5% NaCl Solution

Abstract

Mechanical properties of silicon carbide particle reinforced aluminum alloy 6061 composites with 5% and 10% (SiCp/Al) as well as aluminum alloy 6061 (AA6061) degraded by neutral 3.5% NaCl solution were examined by tensile tests and micro Vickers hardness measurement. The samples were degraded in the neutral 3.5% NaCl solution for a month (≑720 h) at 23°C (room temperature corrosion, RC) and 100°C (high temperature corrosion, HC). It is noted from surface observation of the corrosively degraded samples that the RC-samples (SiCp/Al and AA6061) were degraded by pitting around intermetallic compounds and SiC particles while corrosive degradation of the HC-samples was caused by synergy effect of pitting and intergranular corrosion. Corrosion reaction of the RC-samples was limited to their surface but the HC-samples were received severe corrosion damage until inside part. Thereby, mechanical strength of the latter (a maximum of 220 MPa) was lower than that of the former (a maximum of 330 MPa). Reduction of proof stress, σ0.2%, and ultimate tensile strength, σUTS, was greater in the SiCp/Al than in the AA6061 in the case of the same condition. The result to analyze the experimental data regressively showed that reduction of tensile strength for the RC-samples was proportional to the size of pit while tensile strength of the HC-samples was proportional to the ratio of corroded area to cross-section area. The empirical equations to evaluate the mechanical strength of both cases of the corrosively degraded samples (RC- and HC-samples) were proposed.