STRESS CORROSION CRACKING ISSUES IN LIGHT METALS FOR AUTOMOTIVE APPLICATIONS

摘要

The Partnership for New Generation Vehicle has the goal of producing lightweight automobiles that achieve 80 mpg. To accomplish this will require liberal use of Al and Mg alloys such as AA5083 and AZ91D. The corrosion and stress corrosion of alloy AA5083 is controlled by the precipitation of the beta-phase (Al_3Mg_2) at grain boundaries and by the precipitation of the gamma-phase (Mg_(17)Al_(12)) in AZ91D. The beta-phase is anodic to the Al matrix while the gamma-phase is cathodic to the Mg matrix. The effects of crack propagation along grain boundaries with electrochemically active particles is a key factor in the SCC performance of these materials.