Inter-relationship between residual stresses, microstructural evolutions, and mechanical responses of heat-treatable aluminum alloys during welding: a numerical and experimental study

Abstract

Welding of heat treatable aluminum alloys poses a significant challenge due to the formation of unwanted microstructural changes, inferior mechanical properties, and formation of residual stresses (RS). An understanding of the inter-relationship between these aspects is crucial for the successful design of welding procedures. Given the complexity of these materials, a combination of numerical and experimental investigations is necessary to address this interrelationship. In this work, the effect of welding heat input on the post-weld precipitation hardening, changes in mechanical properties, RS formation, and their inter-relationship in different welding regions of the heat treatable AA2024 was numerically and experimentally studied. Two different thicknesses of the base material, 3.5 mm and 6 mm were chosen to investigate the effect of different heat inputs and geometries. The results show that the highest RS are formed in the partially melted zone (PMZ) and heat affected zone (HAZ), with values of 300 MPa and 221 MPa, respectively, for the 6 mm sample, where the mechanical properties and microstructure were most affected. These high tensile RS accelerate the age hardening process of these regions, resulting in 20 HV changes in the PMZ and 14 HV changes in the HAZ in 70 days. The strength of the material due to these microstructural evolutions determined the load bearing of each region and their maximum RS.