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Friction stir welded Mg AZ31B alloy have been investigated. Friction stir welding (FSW) is carried out at different rotational speeds of 900 rpm, 1120 rpm, 1400 rpm and 1800 rpm and with change of tool materials such as High speed steel (HSS) and Stainless steel (SS) at a constant welding speed of 40 mm/min, tilt angle of 2.5 0 and axial force of 5 KN. It is observed In this study, the effect of tool material and rotational speed on microstructure and mechanical properties of that the joint fabricated using SS tool material at a rotational speed of 1120 rpm obtained higher mechanical properties as compared to those of 900 rpm, 1400 rpm and 1800 rpm and also to those of HSS material.

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Aluminium-silicon alloy pins were dry slid in unidirectional and reciprocating sliding against steel counterjiies in a normal pressure range of 0.39-26 MPa and a sliding speed range of 0.6-1.8 m/s. Changing the mode of sliding from unidirectional to reciprocating as well as an increase in reciprocating speed were found to affect wear and seizure resistances adversely. Alloying additions of copper and magnesium to the base metal, on the other hand, were found to improve both of these properties. The temperature rise of the pin during sliding and the mechanical behaviour of the test alloys in compression in a temperature range of 25-300"C and a strain rate range of O.I-lOO/s were recorded and the data incorporated into a qualitative model to account for the wear and seizure behaoiour of the test materials.