Failure Analysis of Incipient Melting in 7075 Aluminum Alloy

Incipient melting is a phenomenon where areas with high local solute content melt before the rest of the material, degrading mechanical and corrosion properties and resulting in material scrapping. After detecting indications of incipient melting as the cause of failure in 7075 aluminum alloy parts (AA7075), a study was launched to determine critical temperature for incipient melting. Samples of AA7075 were solution annealed using temperatures ranging from 870-990˚F. Modified Keller’s reagent along with as-polished images and color etching were used to identify signs of incipient melting such as grain boundary melting, rosettes, and any other microstructural changes. A hardness profile was developed to demonstrate the loss of mechanical properties through the progression of incipient melting.