Effect of Welded Pitch and Number of Pass on Mechanical and Metallurgical Properties of Friction Stir Welded Joints of Magnesium AZ31B-O Alloy

Magnesium have several properties likes light weight, high specific strength, good damping properties and machine ability. That is why it is attractive metal for automobiles and mobile electronics for effective reducing weight. The main aim of the experiment is to study the behavior of Magnesium AZ31B-O alloy when its joints are welded with friction stir welding. So for this purpose we have conducted visual testing, mechanical and metallurgical testing on 5mm thick plates welded by FSW. In this investigation an attempt has been made to study the effect of friction stir welding parameters like welding pitch i.e. combined effect of welding speed rotational speed of tool with single and double pass of tool. Various parameters such as welding speed of 30 mm/min and 45 mm/min with tool speed of 1200 rpm and 1650 rpm has tried with single and double pass. The optimum results are found at 1200 rpm and 45mm/min with double pass because of homogeneous dispersion of material. It is also observed that during single pass excessive heat generation and insufficient material flow occur at higher tool rpm, leading to formation of defects like tunnel defect which ultimately results in failure of weld joints between SZZ and TMAZ.