Influence of Thermomechanical Treatment on Microstructure and Mechanical Properties of High-Strength Aluminum Alloys

摘要

The influence of a thermomechanical treatment (TMT) on the microstructure and the mechanical properties of AlZnMgCu alloys was investigated. The inhomogeneous slip which occurs during the rolling process produced shear-offsets at the grain boundaries and so reduced the effective grain boundary length. In a pure alloy without Fe, Si, and Cr this microstructural modification caused an improvement of various mechanical properties: the tensile ductility increased, as well as lifetime in fatigue tests; the stress corrosion cracking resistance of the alloy was enhanced, and the fracture toughness values were raised; and the fatigue crack propagation behavior in the high crack propagation rate regime was improved. At low crack propagation rates the cracks propagated along slip bands; in this regime the TMT caused a deterioration of the crack propagation behavior. Commercial AlZnMgCu alloys also showed microstructural modifications at the grain boundaries produced by the TMT. These alloys were found to be only slightly affected by the TMT.