PSI - Issue 17

Madhav Raturi et al. / Procedia Structural Integrity 17 (2019) 495–502 Madhav Raturi et al. / Structural Integrity Procedia 00 (2019) 000 – 000

497

3

2. Experimental details

Dissimilar butt friction stir welds of 6.1 mm thick AA6061-T6 and AA2014-T6 were obtained using two different tool pin profiles at different tool rotation and welding speeds. For all the welding in the present study, the AA6061-T6 material was placed on the advancing side (AS), whereas AA2014-T6 was placed on the retreating side (RS) of the weld plates (Fig. 1(a)). Two different tool pin profiles: threaded with three intermittent flat faces (TIF) and truncated square pyramidal shaped (front appearance of trapezoidal tapered) (TPZ) tool pins were used in the present study for dissimilar FSW. The schematic illustration and dimensions of FSW tool pins are shown in Fig. 1(b). The joining of AA6061-AA2014 was carried out with different combinations of pin profiles (TIF, TPZ), tool rotational speed (660, 900, 1200 rpm) and welding speed (36, 63, 98 mm/min) as shown in Table 1. The three specimens each for tensile and notched charpy impact (toughness) testing were cut alternatively from each welded plate using wire electric discharge machining as shown in Fig. 1(a). The detailed dimensions of tensile and toughness samples are also shown in Fig. 1(a).

6

100

25

R6

10

45

2

55

10

TIF tool pin

TPZ tool pin

(All dimensions are in mm)

(a)

(b)

Fig. 1. Schematic representation of (a) tensile, toughness specimens cut from welded plates; (b) TIF and TPZ tool pins.

The Ultimate Tensile Strength (UTS) and impact toughness of three samples from each welded plate for each condition were recorded and the average readings were reported. Tensile testing was performed on Zwick/Roell Z50 universal tensile testing machine (capacity 50 kN) at cross head speed of 0.5 mm/min. Contact type extensometer of 25 mm gauge length was used to record yield strength (at 0.2% offset strain). The impact testing was carried out on Zwick/Roell RKP450 (capacity 300 Joules) impact testing machine. The transverse section of tensile samples were polished (thickness face) and etched using modified Poulton’s reagent before performing tensile test in order to observe the site of failure of the welded joints. Later, the fractured samples were observed under optical microscope to trace the exact location of fracture. The Field Emission Scanning Electron Microscope (FE-SEM) along with the Electron Diffraction Spectroscopy (EDS) was utilized for detailed characterization and analysis of the fracture surfaces.

Table 1. Selected process parameters for dissimilar FSW between AA6061-T6 and AA2014-T6 Sample Pin profile Tool rotation (rpm)

Welding speed (mm/min)

660 900 900 660 660 900 1200 1200

63 36 63 98 36 63 63 36

W1 W2 W3 W4 W5 W6 W7 W8

TIF TIF TIF TIF

TPZ TPZ TPZ TPZ