Sensitization can occur in 5000 series aluminum alloys, particularly under marine environments, leading to undesirable stress corrosion cracking. Ultrasonic impact treatment (UIT) is a severe plastic deformation surface treatment that curbs sensitization. The objectives of this work are to measure mechanical properties of UIT treated sensitized and non-sensitized 5456-H116 Al using microsamples, extracted varying distances from the UIT surface and characterize the controlling phenomenological mechanisms. Fractographic analysis of specimen ductile fracture failure surfaces explains the measured mechanical property variations as a function of sensitization (or not), processing (UIT and Welded), and distance from the UIT treated plate surface.

Micro X-ray tomography is used to characterize secondary Mg particles in 5000 series Al specimens with varying stress triaxiality. The tomography-measured Mg particle geometry, distribution and void behavior are used to identify the controlling ductile fracture mechanisms. These measurements become inputs for models predicting strain to failure.