Comparing the Effect of Prior Exposure on the Durability of Boeing Space, Intelligence, and Weapons Systems LPBF Scalmalloy and LPBF 7A77

The US DoD Inspector General's Audit of the F/A‐18 fleet and the US Government Accountability Office's report into the sustainment of the F35 fleet have focused attention on the effect of the environment on structural integrity. Since Boeing Space, Intelligence, and Weapons Systems (BSI&WS) laser powder bed fusion (LPBF) Scalmalloy and LPBF 7A77, which are both additively manufactured aluminum alloys, are being considered for building limited‐life parts for military aircraft, this paper compares the effect of prior exposure to an aggressive environment on their durability and their equivalent initial damage sizes. We show that, whereas the 7A77 specimens had extensive corrosion after only 14 days of exposure to a 5% salt spray fog environment at 35°C, Scalmalloy showed little evidence of corrosion after 28 days. Subsequent fatigue tests found that 7A77 had a significantly lower fatigue life than Scalmalloy and that its fracture toughness was significantly lower than that of Scalmalloy.