The Effect of Applied Stress and Potential on Corrosion Fatigue Behavior of Sic/7075 Al Metal Matrix Composite

In the NaCl solution, 4 points bending tests were attemped to investigate the eorrosion fatigue behavior of SiC/7075 A1 metal matrix eomposite (MMC) comparing with ordinary matrix A1 alloy (A1 alloy). Time to failure of both MMC and Al alloy deerease with an inerease of loaded stress or applying at more anodic potential, and under the same condition, corrosion fatigue life of MMC was longer than that of Al alloy. The crack initiation and growth in corrosion fatigue process explained by passive region, repassivation process, and dissolution of newly created surface can be monitored by measuring the potential at the open-circuit and the current at the potentiostatic condition. As the results of this technique, it was shown that corrosion fatigue process, fracture morphology, and the site of the crack initiation for MMC was different from them for Al alloy, and the crack occurred from the bottom of pits on the MMC. Current amplitude corresponded to the defect of corrosion fatigue. According to the measurement of current amplitude, it was shown that once corrosion fatigue started, MMC got marked damage, however for almost all the period of corrosion fatigue test, it was resistive.