Properties and optimization of dissimilar aluminum steel CMT welds

Robotic cold metal transfer (CMT) welding was recently suggested as a feasible process for joining of aluminum to steel for automotive applications. To promote an understanding of the process and the effect of process parameters on joint properties for selected sheets, CMT welding experiments have been performed. Commonly used materials in automotive industry, 0.75-mm DX54D+Z galvanized steel and 1.0-mm EN-AW-5754-H111 alloy, have been used in this study. Total number of 16 welds has been obtained using various parameters such as a wire feeding speed, welding speed, and torch deviation distance by means of L16 array Taguchi analysis. The aim of the study is to analyze the microstructure-strength relationship taking into account heat input-intermetallic compound (IMC) layer developed between aluminum and steel after determining the optimum process parameters based on the peak load for mechanically sound weld. Optimum parameters for 1.0-mm thick EN-AW 5754-H111 aluminum alloy to 0.75-mm thick DX54D+Z galvanized steel using the CMT process have been determined for the wire feeding speed range of 4–5 m/min, a welding speed range of 8–10 mm/s, and deviation distance range of 0–1 mm. The IMC layer thickness formed between aluminum and steel varied between 2 to 13 μm for different heat input values. Energy dispersive spectroscopy (EDS) analysis have been done at two different zones, galvanized steel side (IMC layer) and aluminum alloy side. The intermetallic compound layer consisted of two different phases: Fe2Al5 phase formed near the galvanized steel side and FeAl3 phase penetrated towards the Al alloy side.