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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Fig. 8. The relationship between welding time and the nugget diameter, welding currents 14.25 KA.

3.4. Microhardness test The microhardness tests were conducted on both sides of the welding joints, see Fig. 9. Figure 10 represents the distribution of microhardness in the weld nugget area and adjacent areas (BM, HAZ, and FZ). The minimum hardness was measured at HAZ on aluminum side. The fracturing occurs at the HAZ where the lower fracture toughness (Al-Mukhtar 2016, 2015; A. Al-Mukhtar and Doos 2013; A. M. Al-Mukhtar and Doos 2013; Al Mukhtar et al. 2013). By decreasing the differences in hardness in a sample between the steel side and the aluminum side, the tensile force of the joint increases and vice versa, see Table 3.

Table 3. Tensile test results of the selected samples. Run Electrode force N Welding current KA

Welding time Cycle

Tensile force N

9

1500 2100 2100 2400

14.25 12.75 14.25 14.25

40 25 40 40

2040 1788 2540 3210

13 18 27

Fig. 9. Microhardness testing on both sides of joints (hardness load=200 gram).