Microstructural characterizations and mechanical properties in underwater friction stir welding of aluminum and magnesium dissimilar alloys
Introduction
As light alloys with low density, high special strength and good anti-corrosion properties aluminum and magnesium are widely used in transportation and electronic communications industries. In certain applications, the successful welding of dissimilar metals of aluminum and magnesium is advantage for producing lightweight structures, pushing forward the lightweighting technology and the project of energy-saving and emission-reduction [1]. Researchers had tried various fusion welding methods such as gas tungsten arc welding (GTAW), gas metal arc welding (GMAW) [2], laser welding [3] and solid state welding technology such as vacuum diffusion bonding [4] to join Al–Mg. However, these welding methods are not widely used because of the poor weld joint strength caused by pores, cracks and Al–Mg intermetallic compounds with high hardness and low ductility. In addition, some specific process requirements which are difficult to carry out cause these methods limited.
Being different from fusion welding, friction stir welding (FSW) is a solid-state welding process. In the process of FSW, shouldered tool with a pin rotates and moves between sheets of the pieces to be welded and friction heat which is not sufficient to melt the materials generates. In consequence, materials to be welded reach the plastic state and are joined together under the action of stirring and pressure [5], [6]. Naturally, the obvious lower temperature helps FSW to avoid many defects appearing in fusion welding and the nature features FSW owns make it get higher joint strength. All these make FSW be a potential welding technique in dissimilar materials joining. More details about the process of FSW were described in many earlier publications [7], [8], [9], [10], [11].
Recent years, many efforts had been focused on the application of FSW in dissimilar materials such as dissimilar Al alloys [12], [13], [14], dissimilar Mg alloys [15], Al to steel [16], [17], and Al–Mg [18], [19], [20], [21]. Some researchers had tried to weld Al and Mg alloys under water using the method of FSW and got better mechanical properties than in air [22]. While joints of Al alloys and Mg alloys obtained by FSW under water were sound with good mechanical properties, the details of microstructural evolution of dissimilar joints of Al and Mg alloys have not been fully understood. In this paper, 6013 Al alloy and AZ31 Mg alloy were welded by FSW under water. The microstructure, distribution of elements, hardness, tensile strength and fracture feature of the joints were investigated to make a comprehensive analysis of the microstructures and mechanical properties of the FSW joints of 6013 Al alloy and AZ31 Mg alloy.
Section snippets
Material and experimental procedures
Commercial available base materials (BM) AA6013 aluminum alloy and AZ31 magnesium alloy sheets (100 × 90 × 2.5 mm) were welded in the study. Their chemical compositions and mechanical properties are listed in Table 1. The weld process was done under water at a FSW-3LM-002 machine produced by China Friction Stir Welding Center in this experiment. The shouldered tool which was made of H13 steel was 16 mm in diameter and concave, with a 2.5 mm long and 5 mm in diameter threaded cylindrical probe. During
Appearances and microstructures
Fig. 1 shows the surface appearance of the friction-stir joint of Al 6013 and Mg AZ31 performed under water. It can be seen that sound weld without obvious defects such as cracks or tunnel type defects was obtained when rotation speed was 1200 rpm and travel speed was 80 mm/min with the pin moving along the center. This is contrary to some other researcher’s result. Yan et al. [23] reported that if rotating pin traveled along the butt line between the two base materials cracks developed.
A
Conclusions
6013 Al alloy and AZ31 Mg alloy were FS-welded under water in this study and from the above investigations, the main conclusions can be summarized:
- (1)
Sound welding with good mechanical properties was produced between 6013 Al alloy and AZ31 Mg alloy through FSW under water with the welding speed of 80 mm/min and rotation speed of 1200 rpm.
- (2)
EPMA images show that elements of Al and Mg are stirred together and mixture structure form in the stir zone. The EDS analysis indicates that the mixture structures
References (29)
- et al.
Factors affecting the properties of friction stir welds between aluminum and magnesium alloys
Mater Sci Eng A
(2012) - et al.
Microstructure characteristics in TIG welded joint of Mg/Al dissimilar materials
Mater Lett
(2007) - et al.
Suppression of intermetallic reaction layer formation by controlling heat flow in dissimilar joining of steel and aluminum alloy
Mater Sci Eng A
(2007) - et al.
Effect of Zn alloy interlayer on interface microstructure and strength of diffusion-bonded Mg–Al joints
Scr Mater
(2008) - et al.
Microstructure of friction stir welding of aluminium alloy to magnesium alloy
Scr Mater
(2009) - et al.
Dissimilar friction stir welding between magnesium and aluminum alloys
Mater Lett
(2008) - et al.
Microstructure and mechanical properties as a function of rotation speed in underwater friction stir welded aluminum alloy joints
Mater Des
(2011) - et al.
Microstructure and mechanical properties of spray formed 7055 aluminum alloy by underwater friction stir welding
Mater Des
(2014) - et al.
Materials selection in design of structures and engines of supersonic aircrafts: a review
Mater Des
(2013) - et al.
Solid-state flow visualization in the friction-stir welding of 2024 Al to 6061 Al
Scr Mater
(1999)
The improvement of mechanical properties of friction-stir-welded A356 Al alloy
Mater Sci Eng A
Factors affecting the properties of friction stir welds between aluminum and magnesium alloys
Mater Sci Eng A
Influence of intermetallic phases and Kirkendall-porosity on the mechanical properties of joints between steel and aluminium alloys
Mater Sci Eng A
Joining of aluminum alloy to steel by friction stir welding
J Mater Process Technol
Cited by (147)
Material flow during dissimilar friction stir welding of Al/Mg alloys
2024, International Journal of Mechanical SciencesRegulating solute partitioning via submerged friction stirring technology for improving corrosion resistance in an Al–Mg alloy
2024, Materials CharacterizationA review on friction stir butt welding of aluminum with magnesium: A new insight on joining mechanisms by interfacial enhancement
2023, Journal of Materials Research and TechnologyExperimental investigations on cryogenic friction-stir welding of similar ZE42 magnesium alloys
2023, Alexandria Engineering Journal