Unveiling Liquation and Segregation Induced Failure Mechanism in Thick Dissimilar Aluminum Alloy Electron-Beam Welds

Abstract

This study presents new findings on the underlying failure mechanism of thick dissimilar electron-beam (EB) welds through a study on the AA 2219-AA 5083 pair. Contrary to the prior studies on EB welding of thin Al alloys, where liquation in the grain boundaries (GBs) in the partially melted zone (PMZ) was not observed, the present investigation for thick EB welds reports both liquation and increased segregation of Cu in the PMZ. The work is thus directed towards understanding the unusual observation in the PMZ of thick EB weld through investigation of the microstructural variation across the various regions of the produced weld. The microstructural results are correlated with the mechanical properties of the weld, i.e., hardness variation and tensile response. Results of this investigation suggest that unlike the convention that EB welding produces sound dissimilar Al welds, the weld performance for thick EB Al welds is affected by the heat input, the associated cooling rates, and most importantly by the base material thickness. Extensive liquation and Cu segregation induced failure in the PMZ on the AA 2219 side of the dissimilar weld. The underlying failure mechanism is explained through a heat-transfer analysis. Beyond a certain plate thickness, the heat transfer changes from two to three-dimensional. As a result, retarded cooling promotes liquation and Cu segregation in thick EB welds.

Dissimilar Friction Stir Welding of AA2519 and AA5182

“…This indicates that joints are free of defects and the achieved joint efficiency is around 100% (based on alloy AA5182). This is much higher than what can be achieved with electron beam [5,32,33] and TIG [8] welding processes. The presented data agree with the results obtained in dissimilar FSWed joints of AA2219 and AA5083 [6,13,14,[16][17][18].…”

Microstructure Evolution and Mechanical Properties of Thick 2219 Aluminum Alloy Welded Joints by Electron-Beam Welding

“…In addition, there were some θ-Al 2 Cu particles in the WZ and Al-Cu eutectic in the HAZ. Mastanaiah et al found that the θ-Al 2 Cu particles precipitated from α-Al matrix destroyed the integrity and induced the initiation of cracks during the deformation process [17]. Thus, the 2219 joint showed a lower elongation.…”

“…Fujii et al [16] investigated the relation between pores and bubble generation. He found that the bubbles were formed through a reaction between the molten Al and Al 2 O 3 forming Al 2 O. Mastanaiah et al [17] reported that the extensive liquation and segregation of Cu in the partially melted zone (PMZ) increased in the thick-plate EBW, which resulted in the failure of PMZ on the 2219Al side of the 2219/5083 joint. S.A. Hosseini et al [11] evaluated the hot cracking sensitivity of 2024 joint by EBW and investigated the effects of heat input on the hot cracking.…”