Load induced inhomogeneous plastic deformations in welded aluminium joints

In this work, the influence of varying heat input related to different welding processes (gas tungsten arc welding (GTAW), gas metal arc welding (GMAW) and electron beam) on the structure and property of the weld near heat-affected zone was investigated using a cold-formed and a precipitation-hardened aluminium alloy. Multiple tensile tests on welded samples were performed in order to comprehend the correlation between heat-induced local softening and dissipation of precipitations and the local elastic and plastic deformation behaviour under tensile loading. During these testings, the transient deformation was measured using an optical 3D deformation measuring system based on grey-scale pattern recognition. Additionally, material characterizations, such as two-dimensional hardness measurements using the instrumented indentation test, were carried out. Both aluminium alloys showed a different strain distribution under tensile loading. In addition, finite element (FE) models were developed to describe the plastic deformation behaviour. In finely meshed models, the distribution of the local yield strength was set corresponding to measurements using instrumented indentation. That way, the differences between models which include a softening area and those that do not could be shown.