Stress Corrosion Cracking Behavior of Wrought Magnesium Alloy AZ31 and AZ61 under Controlled Cathodic Potentials

摘要

The stress corrosion cracking (SCC) tests were performed using the wrought magnesium alloys,AZ31,AZ61 and T5 heat treated AZ61 (AZ61-T5) in a NaCl solution under the controlled cathodic potential in order to investigate the effects of the anodic dissolution and the hydrogen embrittlement on the SCC behavior.The crack growth rate (da/dt) of AZ31 was faster than those of AZ61 and AZ61-T5 under the same cathodic potential.The threshold stress intensity factor for SCC propagation (KISCC) of AZ31 was lower than those of AZ61 and AZ61-T5,and KISCC of AZ61-T5 was lower than that of AZ61,which is attributed to the difference of resistance to anodic dissolution.In AZ31 and AZ61,KISCC under the cathodic potential of -2.5 V was higher than those under the other cathodic potentials.In all materials,KISCC under the cathodic potential of -1.4 V was lower than those under the cathodic potentials of -3.0 V and -4.0 V.By the observations on the fracture surfaces after the SCC tests,less corrosion products were observed on the fracture surfaces under the cathodic potentials of -3.0 V and -4.0 V than on the fracture surfaces under the cathodic potential of -1.4 V.