Microstructural Characterization of Ultrasonically Welded Aluminum

Abstract

The microstructure and mechanical properties of ultrasonically welded AA6111-T4 specimens are discussed. The effects of welding time on the mechanical properties of welded joints are investigated. A longer welding time results in a more continuous welded interface and higher yield and fracture strengths. Accordingly, fatigue properties of the welded specimens with longer welding times are improved. The results of electron microscopy on the cross section of ultrasonically welded joints show three distinct zones: weld zone, weld affected zone and compression zone each with a distinct microstructure. TEM results show nanocrystalline grains along with second phase particles in the range of 15–25 nm in the weld zone. Flow patterns consistent with the geometry of weld–tip were observed at the weld interface.