Research on Multi-artificial Aging Applied to Aluminum Alloy 7150 Plate

摘要

The AA 7150-T351, in the form of 40 mm thick plates, was subjected to single-stage aging leading to peak aged condition, and two selected multi-artificial aging treatments leading to the over aged conditions. The microstructural differences along the thickness direction of the AA 7150-T351 plate were investigated using OM and electron backscatter diffraction (EBSD) technique, and the microstructural characterization was studied at different stages of multi-artificial ageing process by transmission electron microscopy. Tensile properties and electrical conductivity measurements were used to evaluate the property homogeneity along the thickness direction of the plate under various artificial aging tempers. It was revealed that the microstructural features and tensile property are inhomogeneous in different layers along the thickness direction, and both grain structure and tensile property exhibit appreciable anisotropy at the same thickness layer. The volume fraction of recrystallized grain of T351 plate in the near surface layer is higher than that in the center layer remarkably. It is also shown that two selected multi-artificial aging tempers can provide optimal precipitates in matrix and at grain boundaries, which gives rise to a combination of high strength and stress corrosion cracking (SCC) resistance in such materials.