Friction welding of AA6061 to AISI 4340 using silver interlayer SURESH D. MESHRAM＊, G. MADHUSUDHAN REDDY

Study of plastic flow on intermetallic compounds formation in friction welding of aluminum alloy to stainless steel

Aluminum alloy/steel hybrid components are receiving more and more attention in recent years due to their great potential in reducing weight while maintaining the mechanical properties of the structure. Inertia friction welding was performed to join 2219 aluminum alloy (Al alloy) bar to 304 stainless steel bar. The effects of welding parameters on the evolution of intermetallic compounds (IMCs) and tensile strength of the joints were investigated. High-quality welded joints can be obtained at the parameters combination of the medium friction pressure (120 MPa) and low rotational speed (1100 rpm) from the experimental study. Microstructural analyses indicated that the enrichment of Cu element at the friction interface formed Al2Cu IMCs instead of Fe-Al IMCs, which was usually reported to exist at the Al alloy/steel friction welded interface. The formation of the Al2Cu IMCs layer was mainly attributed to the accumulation of Al2Cu (precipitate in 2219 Al alloy base metal) at the wavy surface of the steel, significantly promoting the growth of Al2Cu by the subsequent precipitation process. However, cracks could easily occur in a thicker Al2Cu IMCs layer at a high heat input, which seriously deteriorated the mechanical properties of joints. Therefore, the massive formation of the Al2Cu IMCs layer should be suppressed by controlling the welding parameters to avoid any internal cracks at the weld interface.

Interfacial microstructural characterization and mechanical properties of inertia friction welding of 2219 aluminum alloy to 304 stainless steel

In this work, the tensile-shear mechanical behaviors of friction stir spot weld and adhesive hybrid joint were performed from both numerical and experimental viewpoints. Weld through (WT) and flow in (FI) processes were studied in this research. The focus was to evaluate joint defects, tensile-shear failure load (TSFL), failure energy, failure mode and stress distribution of the joint. In FI joints, keyhole and hook defects appeared in the weld zone and the areas of material removed from the base metal were filled with adhesive. In the WT joints, the adhesive layer close to the weld zone was carbonized due to the welding heat. Meanwhile, under the rotating movement of welding tool, the adhesive impurities entered the stirring zone (SZ) and heat affected zone (HAZ) of the weld, which decreased mechanical performances of WT joints. Compared to the friction stir spot welding (FSSW) joint, the TSFL value, stiffness and failure energy of FI joint were increased by 2.7, 1.1 and 8.14 times, respectively. In order to study the stress distribution of the joints, a finite element (FE) model, which considered the weld structure and mechanical properties of weld regions, was implemented. Moreover, the adhesive layer was simplified by the cohesive zone model (CZM). FE results show that the FI process effectively decreases the stress concentration of the weld edge from 243.09 to 15.5 MPa, under the 2 kN tensile load. The weld can block the adhesive crack propagation, and the adhesive optimized the stress distribution of FI joints through a synergistic effect. So, the use of FI process for aluminum alloy connection is strongly recommended, especially in crucial structure areas.

N. Ramanaiah

Papers

Dissimilar metals AISI 304 steel and AA 2219 aluminium alloy joining by friction welding method