Tube spinnability of AA2024 and 7075 aluminum alloys

Tube spinnability is defined as the maximum thickness reduction before either fracture or buckling under the given roller geometry, feed rate, and the speed of the mandrel during the tube spinning of a metal. There are two ways to experimentally determine the tube spinnability of the full-annealed and solution-treated AA 2024 and 7075 aluminum alloys. One is to reduce the thickness stepwise to the final thickness without failure of the tube. The other is the one-path spinning with continuous reduction in wall thickness of preform from initial to the final thickness without buckling to determine the achieved maximum reduction. Using continuous reduction test, the determined macro-spinnability of fully-annealed AA 2024 Al alloys is 75% and that of 7075 Al is 74%. But, when examined by scanning electron microscope, the deformation tongue is visible on the outer surface as the thickness reduction exceeds 50% for both fully annealed 2024 and 7075 Al alloys. However, for both solution-treated 2024 and 7075 tubes, the spinnability is lower than that of fully-annealed conditions. The discrepancy between the reduction test and microscopic spinnability will be discussed in terms of the microstructure and the mechanical properties.