MICROSTRUCTURE AND PROPERTIES OF FRICTION STIR BUTT-WELDED MAGNESIUM CASTING ALLOYS

The article presents results of testing the quality of FSW welded joints made in plates of various magnesium casting alloys, including MCMgAl9Znl (AZ91), MCMgRe3Zn2Zr (ZRE1), MCMgRe2Ag2Zr (MSR-B) and MCMgY4Re3Zr (WE43). In this paper, all results for magnesium casting alloy AZ91 are presented, whereas for other alloys (ZRE1, MSR-B and WE43) only selected testing results for best parameters have been chosen and shown. Butt joints were produced on the friction welding machine built on the base of the conventional vertical milling machine. Quality assessment included the visual inspection, temperature measurements in welding region, tensile strength testing, analysis of the weld structure, hardness, weld force and torque measurements. Research aimed at the recognition of the FSW abilities to weld cast magnesium alloys, the influence of the welding conditions on the welds' properties as well as their structures. The research results have revealed that cast magnesium alloys are weldable using FSW process - it is possible to produce joints of very good quality in relatively narrow range of parameters and the strength of the joints is satisfactory. In order to acquire joints of the best quality it is recommended that workpieces should be rigidly clamped and the welding speed should be limited. The best mechanical properties have been obtained for friction with rotation speed of 355 rpm.