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Friction stir welding of UK Ministry of Defence Def Stan 95-22 7017 aluminium alloy (Al, 4.5%Zn, 2.0%Mg) armour plate was evaluated by studying the mechanical properties and cracking of welded joints. Initially plate of 10 mm thickness, locally reduced to 6.35 mm to suit the welding tool, and subsequently plate of 75 mm thickness cut and ground to 6.35 mm (so maintaining original microstructure) was welded, using different combinations of tool and welding speeds, and compared with pulsed MIG welded plate. The welded joints were characterised by studies of stress corrosion and liquation cracking, exfoliation in the HAZ, hardness (surface and mid-section), ultimate tensile strength, 2% proof strength, elongation, and microstructure. The influence of postweld ageing was also studied.

2nd International Symposium, 26-28 Jun 2000, Session 3, Paper 02