Abstract
Friction stir welding is a relatively new joining technique particularly for aluminium and magnesium alloys that are difficult to joint with fusion welding methods. In this study, rolled AZ31 magnesium alloy was joined by friction stir welding method in 960, 1964 and 2880 rpm rotational speeds and in 10 and 20 mm min^-1 transverse speeds. During the welding process, due to the low temperature occurring in low rotations, a coarser surface was obtained. Thanks to the microstructural refinement, the hardness of the stir zone was observed lower compared with the hardness of the parent material due to the temperature released by friction. The fractures mostly occurred at the heat affected zone. The maximum tensile strength of joint reached 93 % of that of base materials, at the 1964 rpm rotational speed and 20 mm min^-1 transverse speed.

Key words
magnesium alloys, hardness, scanning electron microscopy, friction stir welding

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