Friction Stir Welding of Tailored Blanks of Aluminum and Magnesium Alloys

Abstract

The following paper describes a feasibility study of butt joining friction stir welding between aluminum alloy AA6016 and magnesium alloys AZ91 and AM50. Because of the variety of inimitable properties according to lightweight design and constructions, the interest in aluminum and magnesium alloys is increasing in many fields of industry. Due to the low solubility of aluminum in magnesium and inverse, these alloys tend to the formation of intermetallic phases during the joining process. This leads to an increasing micro hardness within the seam, which should be avoided. By the use of joining methods with low process temperatures, the formation of intermetallic phases is reduced. According to this circumstance, friction stir welding is an excellent alternative to fusion welding techniques used to join this alloys. The main welding process variables were exposed in the studies of similar butt joints of Al/Al and Mg/Mg. These were examined in connection to their transferability to the dissimilar joints and tailored blanks. Furthermore, the influence of different tool geometry on seam quality was investigated. The effect of process variables (mainly welding speed and revolution speed) were correlated to the results of tensile strength test. The welded samples were assayed in the presence of intermetallic phases.

Growth kinetics of Al–Mg intermetallics during post-weld annealing treatment

“…The thickness of the IMC layer increased with the offset position on the Al side and TEM results showed that the IMC layer was composed of b-Al 3 Mg 2 (near Al side) and g-Al 12 Mg 17 (near Mg side). 10,11 The result also showed that the thickness of the b-Al 3 Mg 2 IMC is larger than that of g-Al 12 Mg 17 IMC and that the formation and growth of the IMC layers are controlled by the reaction diffusion. Le et al 12 carried out the diffusion coating treatment in molten salts at lower temperatures to investigate the interdiffusion kinetic of the intermetallic coatings.…”

The Influence of Ultrasound Enhancement during Friction Stir Welding of Aluminum to Steel

“…The strength of these dissimilar joints is strongly related to the formation of intermetallic (IM) phases with a brittle character while welding. Despite the relatively low process temperature of friction stir welding such intermetallics occur for every dissimilar material combination such as aluminum/magnesium [6][7][8], aluminum/cooper [9,10] or aluminum/steel [11,12]. Most of the literature showed, that a small IMphase leads to highest tensile strengths and resistance under cyclic loading [4,5,13,14].…”

Review of research progress on aluminium–magnesium dissimilar friction stir welding

“…In one of the initial developments by Sato et al, FSW butt joints between Al alloy 1050 and Mg alloy AZ31 were successfully produced [21] by placing AZ31 at the AS and 1050 at the RS, while exchanging their positions led to unsuccessful joining. Other subsequent reports have also suggested similar position setup [11, 24, 28, 30, 36, 40, 41, 44]. However, the majority of studies have advocated that placing aluminium on the AS and magnesium on the RS gives the best metallurgical quality [12, 20, 22, 23, 25-27, 29, 31, 32, 35, 37-39, 42, 43, 46, 49].…”

“…There are numerous advantages offered by dissimilar welding, such as cost reduction, higher energy efficiency, optimisation of materials and the ability to 'tailor' the materials design to suit optimal properties in specific areas. These advantages have been well exploited in the automotive industry by way of stamped dissimilar sheet body structures, commonly referred to as tailor-welded blanks [11][12][13][14]. Further developments in dissimilar joining technology have opened up new frontiers in numerous industrial applications such as in automotive, aircraft engine turbines, nuclear reactor materials and X-ray equipment components [10].…”