Abstract
The joining of magnesium alloys with conventional fusion welding methods often causes porosity and hot cracking defects. The use of friction stir welding, a solid-state welding technique for joining Mg alloys, solves these problems. In this study, AZ31B Mg sheets with 3 mm in thickness were joined by friction stir welding at a constant feed rate (50 mm min^–1) and different tool rotational speeds (900 and 1400 rpm), and different tool tilt angles (0° and 1.5°) using tapered pin. Tensile strength and microhardness tests were carried out to examine the mechanical properties of the welded specimens. The microstructures of the welded zone were analyzed by obtaining optical microscopy and scanning electron microscopy images. According to the tensile test results, specimen welded at 50 mm min^–1 feed rate, 900 rpm tool rotational speed, and 1.5° tool tilt angle showed the highest welding strength value 176.03 MPa.

Key words
friction stir welding, magnesium alloys, welding parameters, microstructure, tensile strength

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