Issue 37

C. Patil et alii, Frattura ed Integrità Strutturale, 37 (2016) 325-332; DOI: 10.3221/IGF-ESIS.37.43

Transverse Speed (mm/min)

FSW Sample No.

Rotation Speed (RPM)

Impression (d) (mm)

BHN

A B C D E

900 900 900 800 800 800

30 35 40 30 35 40 30 35 40 35

1.62 1.90 1.80 1.71 1.62 1.70 2.10 1.70 2.80 2.20 2.50 2.11

121 87.4 97.4 108 121 109 71.4 109 40.0 65.0 50.1 70.7

F

G H

1000 1000

A1 A4 B1 B2

700 650

- -

- -

Table II : Brinell hardness Test Result.

R ESULTS AND DISCUSSION

I

n heat treatable alloys, the precipitates only impart strength to the alloy. Dissolution of these strengthening precipitates weakens the mechanical properties of weld joints. In all the FSW joints, the temperature experienced during welding can induce an over ageing of the precipitate particle, resulting in decrease of mechanical characteristics. Actually, by inspecting hardness of FSW joints as shown in Fig. 5-6, the hardness values in all welded samples are reduced compared with base metal, this means that the generated heat during FSW causes softening of the welded area due to dissolution of precipitates (Fig. 7a).

Figure 5 : Effect of transverse speed on hardness for similar FSW & TIG joints.

329