PSI- Issue 9

Mohammad Jameel Zedan et al. / Procedia Structural Integrity 9 (2018) 37–46 Mohammad Jameel Zedan, et al. / Structural Integrity Procedia 00 (2018) 000–000

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is suitable for RSW and mass production. Therefore, the low carbon steel 1008 was chosen (Nikolaevich et al. 2014). As a technique for joining sheet metal components, RSW is much quicker than riveting. Less skill is required, resulting in lower labor costs since the process is largely automated (Timings 2008). Welding of aluminum alloys with steel alloys by resistance spot welding is a major challenge because of the different physical properties between them (Mathers 2012). The previous studies of aluminum and steel RSW focused on the mechanical properties and the weldability parameters. Also, the microstructural effects have been investigated. Results of aluminum-steel RSW shown that the layers of Fe 4 Al 13 or FeAl 3 phase with needle-like will be formed in the side of the aluminum alloy. Also, Fe 2 Al 5 phase with lath-like in the side of steel is presented. The tensile shear crack started at the interfacial intermetallic compound layer (Zhang et al. 2011). The using of zinc layer in the welding process will improve the welding. Because the melting and evaporation of the zinc layer will reduce the intermetallic compound layer (IMC) (Arghavani, Movahedi, and Kokabi 2016). Hence, it improves the mechanical properties and enhancing fracture toughness. The wider IMC weakened the joint strength (Sun et al. 2016). The fracture morphology of A5052-DP 600 joints shows an elongated in weld nugget with dimple fracture (Chen et al. 2016). Three major fracture mechanisms led to three failure modes have been identified (Chen et al. 2017). Semi brittle or brittle fracture in IMC layer, a ductile fracture in the aluminum fusion zone (FZ) and ductile fracture in the aluminum heat affected zone (HAZ). The latter, causes the interfacial failure, thickness failure, and button pullout failure. The fracturing of spot welds has also been discussed in Refs. (Al-Mukhtar 2015, 2016; A. Al-Mukhtar and Doos 2013; A. M. Al-Mukhtar and Doos 2013; Daws, Al-Douri, and Al-Mukhtar 2003). In this study, the thermal expansion has been treated since it’s preventing the successful RS welding between aluminum alloy 5052 and low carbon steel 1008. Therefore, a new method has been presented to overcome the heat dissipation and to produce suitable welding. The effects of welding parameters on the joints strength and weld nugget area were investigated. The interfacial microstructure and micro hardness of the welded area were studied. 2. Experimental procedure The materials 1008 low carbon steel, and 5052 aluminum alloy have been used with thickness 0.76 mm, and 0.82 mm, respectively. The chemical compositions and mechanical properties of the materials used are listed in the tables 1, and 2, respectively. The dissimilar samples were machined to the size of 100×25 mm, see Fig. 1. Before welding, the metals samples were cleaned by degreasing with acetone and grinding by abrasive paper.

Table 1. Chemical compositions of low carbon steel and aluminum alloy sheets

Compositions %

C%

Si%

Mn% P% 0.197 0.006

S%

Cr%

Mo% 0.004

Ni%

Cu%

V%

Fe%

Low carbon steel 1008

0.049

0.041

0.003 0.032 Mg% Cr%

0.026 0.11

0.001 Bal.

Compositions %

Si%

Fe%

Cu%

Mn%

Ni%

Ti% 0.02

V%

Li%

Al%

Aluminum alloy 5052

0.161

0.537

0.025 0.058

2.31

0.255

0.007

0.015 0.062 Bal.

Table 2. Mechanical properties of steel alloy and aluminum alloy sheets. Metals Standard tensile strength (MPa)

Experimental tensile strength (MPa)

1008 Low carbon steel 5052 Aluminium alloy

340 290

341 298

The welding current 11.25-14.25 kA, time 25- 40 cycles, and electrode force from 1500- 2400 N have been used. The squeeze and hold time was maintained for 99 cycle. The electrodes flat tip with diameter 11 mm has been used.