Corrosion Effect on Mechanical Properties of Stamped Al Alloy 6451 for Auto Applications

A stamped Al Alloy 6451Al Alloy 6451 containing 0.75 wt% Si used for outer panels of automotiveAutomotive body closures was tested for mechanicalMechanical performance by comparing uncorroded and corroded specimens subjected to immersion corrosionCorrosion following exposure to a 5.5 wt% NaCl saltwater solution. The mechanical propertiesMechanical properties including ultimate tensile strength (UTS), yieldYield strength (YS), and elongation (ef) were evaluated by tensile testing. Following the exposure to a 5.5 wt% NaCl saltwater solution, the stamped alloyAlloys 6451 exhibited a significant decrease of both its UTS and YS to 141.82 and 70.02 MPa from 161.54 and 86.82 MPa, by 12.2% and 19.4%, respectively. Similarly, the ef of the Al alloyAl alloys decreased to 14.62% from 16.23 by 9.9%. The microstructureMicrostructure observation indicated that the presence of corrosionCorrosion pits on the surfaceSurface of the corroded alloyAlloys might promote the crack initiation and growth.