Analysis of possible shipbuilding application of friction stir welding (FSW) method to joining elements made of AlZn5Mg1 alloy

In industrial practice the welding of Al- alloys is usually performed under pure argon shielding by means of MIG or TIG methods. In recent years new joining techniques such as friction stir welding (FSW) have appeared. Joints of EN AW-7020 T6 alloy elements welded by using FSW method have been tested. Results of static tensile tests, transverse bending tests as well as tests on stress corrosion susceptibility are presented. Parameters of friction welding (FSW) applied to joints of plates made of AlZn5Mg1[7020] alloy are given. Stress corrosion tests have been performed by using slow-strain-rate testing method (SSRT) in compliance with PN-EN ISO 7539-7 standard. The tests were conducted in air and 3.5% NaCl water solution. The following parameters have been measured during the tests: time to failure - T [h], maximum failure load - F [N], fracture energy (area under stress-elongation curve) - E [MJ/m³], relative elongation of specimen - A₁₀ [%], maximum tensile stress - R [MPa], as well as percentage reduction of area - Z [%]. On the basis of the obtained test results it was concluded that the joints welded by means of FSW method show good resistance to stress corrosion at satsifactory strength properties, which indicates that application of friction welding by using FSW method in shipbuilding industry is purposeful.