Stress-corrosion cracking susceptibility of various product forms of aluminum alloy 2519

Aluminum alloy 2519 is the main structural alloy for the Advanced Amphibious Assault Vehicle (AAAV). A potential drawback to the use of 2519, particularly for an amphibious vehicle, is its susceptibility to corrosion. General corrosion, which is largely in the form of pitting, may reduce the effective life of the system, while stress-corrosion cracking (SCC) of any high strength aluminum alloy can lead to catastrophic failure. Therefore, an evaluation of the SCC susceptibility of various 2519 product forms was performed. Plate, extrusions, ring roll forgings, and weldments all exhibited excellent SCC resistance as measured by a series of standard ASTM tests. Multi-axis hand forgings were the only product forms that exhibited SCC susceptibility, and this susceptibility was remedied via the use of a specifically designed heat treatment. While all product forms passed the prescribed SCC tests, each exhibited a significant reduction in strength after simultaneous exposure to both stress and the saline corrosion environment. Such behavior was not apparent when the exposure was limited to the corrosion media alone. That is, while resistant to SCC, the load-bearing capacities of all products tested are somewhat degraded during concurrent exposure to stress and corrosive media by a mechanism that includes pitting. This article will discuss the effort that was conducted by the National Center for Excellence in Meta working Technology (NCEMT) to evaluate the SCC susceptibility of 2519 in various product forms and tempers.