Study On Stress Corrosion Cracking Behavior Of Magnesium Alloy With Different PH Values And Temperature

Recently, magnesium alloys have received extensive recognition because of their stress corrosion cracking resistance problem. Nowadays, the researchers did a large of studies on the stress corrosion cracking and protective method, which broadened the application of magnesium alloys to some extent. With the development of studies, people would like to understand the stress corrosion cracking sensitivities in corrosion solution, in order to prevent the huge disaster caused by stress corrosion cracking in production and daily life. The factors to the stress corrosion sensitivities are pH values, temperature, solution concentration and strain rate. In this paper, the stress corrosion cracking behavior of AZ31B magnesium alloy is systematically studied, and the influence of different pH values and temperature to the stress corrosion cracking sensitivities are discuss in the paper, too. The stress corrosion behavior of the extruded magnesium alloy AZ31B in NaCl solutions with different pH ranging from2to12and different temperature change from40℃to60℃are investigated by using slow strain rate tensile(SSRT), electrochemical workstation and SEM. The results indicate that the SCC susceptibility and static corrosion rate have all declined. The main results can be concluded as follows:1. The static corrosion rate and stress corrosion cracking susceptibility go down with the increasing pH values from2to12.2. The main crack source is caused by chioride ion pitting corrosion, the tensile fracture of multiple gap shows that the stress corrosion is characterised by many crack sources, and the tensile stress accelerates the corrosion rate.3. Temperature has a serious influence on the stress corrosion cracking of magnesium. The static corrosion rate and stress corrosion cracking susceptibility go down with the increasing pH values from40℃to50℃, the SCC susceptibility is40℃>50℃>60℃.4. There are so many same features of the fracture both in different temperature and pH values. A lots of second cracking are exist, which are parallel to the fracture and perpendicular to the tensile direction. The number of the second cracking are increasing with the increasing temperature values. When the temperature reach to a high level, some of the second cracking connected with each to growing up a deep one.5. The fractures both in the different pH values and temperature are all flat with river shape pattern, and there exist a mount of stress corrosion cracking along the edge of the fracture. The fracture in the high temperature value have a little tare trustum of a pyramid. It seems that the temperature promote the source of crack extension in the same plane.6. The fracture of slow strain rate tensile are all transgranular cleavage fracture both in different pH values and in different temperature conditions.