Friction Stir Lap Welding of Magnesium Alloy to Steel: A Preliminary Investigation

Abstract

An initial study was made to evaluate the feasibility of joining magnesium alloy AZ31 sheet to galvanized steel sheet in a lap configuration using friction stir welding (FSW). Two different automotive sheet steels were used for comparative evaluation of the dissimilar joining potential: a 0.8 mm thick, electrogalvanized (EG) mild steel, and a 1.5 mm thick hot-dipped galvanized (HDG) high-strength, low-alloy (HSLA) steel. These steels were joined to 2.33 mm thick AZ31B magnesium sheet. A single FSW tool design was used for both dissimilar welds, and the process parameters were kept the same. The average peak load for the AZ31-1.5 mm steel weld joint in lap shear mode was found to be 6.3 ± 1.0 kN. For the AZ31-0.8 mm steel weld, joint strength was 5.1 ± 1.5 kN. Microstructural investigation indicates melting of the Zn coating present on the steel sheets, and subsequent alloying with the Mg sheet resulted in the formation of a solidified Zn-Mg alloy layer.

Laser Keyhole Welding of Dissimilar Ti-6Al-4V Titanium Alloy to AZ31B Magnesium Alloy

“…[7][8][9][10][11][12][13] Laser gas tungsten arc (GTA) hybrid welding has been attempted of the AZ31B alloy to 304 stainless steel and mild steel in lap configuration with the AZ31B alloy on the top. [7,8] The results indicated that the defect-free interfacial layer can be obtained, although the joining strength is poor.…”

“…Obviously, the more precise heat input during laser welding is responsible for increasing the joint strength compared with laser-GTA hybrid welding. A solid-state welding technique, FSW, was also introduced to join a magnesium alloy to steel, including lap configuration with the magnesium alloy on the top [11][12][13] and butt configuration. [14] The results show that the maximum joining strength can reach 70 to 80 pct of the magnesium substrate.…”

Comparative study on microstructure and mechanical properties of laser welded–brazed Mg/mild steel and Mg/stainless steel joints

“…However, the average strength of Mg/stainless steel lap joints was much higher than that of Mg/mild steel joints reaching 270 N/mm, representing 82.4% joint efficiency relative to the Mg alloy base metal. The joint efficiency values were obtained by dividing fracture load of laser welded-brazed specimen by the fracture load of the base metal for the same size tensile specimen [25,26]. The joint strength in previous studies achieved using resistance spot welding (RSW) [11], FSW [26] and laser conduction welding (LCW) [27] was indicated by three dashed lines, which were lower than that of Mg/stainless steel in our current result.…”

Research on laser welding-brazing of dissimilar Mg alloy and stainless steel

“…Recently, solid state joining process, friction stir welding (FSW) was tried to join Mg alloy to steel [6][7][8][9]. Results show the good joining strength can be obtained, which reaches 70-80 % of the Mg substrate.…”