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In this paper, grey relational analysis combined with Taguchi method has been used to evaluate the weld ability of AZ31B magnesium alloy by FSW process. The L9 Taguchi design considering an orthogonal array consists of 3 factors and 3 levels was used for experimentation. The rotational speed of tool, transverse speed and angle of tilt of the tool are selected as welding parameters. The welding parameters influence on responses namely Ultimate Tensile Strength (UTS) and hardness has been analyzed using ANOVA. The analysis results showed transverse speed as the predominant welding parameter affecting tensile strength, hardness, and weld quality. Confirmation test results showed that grey relational analysis along with Taguchi method yielded better results in the optimization of welding parameters in FSW of AZ31B magnesium alloy. [ABSTRACT FROM AUTHOR]

Friction stir welding (FSW) is a solid-state joining process producing high-quality welds with lower residual stresses and improved mechanical properties. Underwater FSW is a variant of FSW process which controls heat conduction and dissipation along the weld line improving the joint properties. The feasibility of underwater friction stir welding of AA 5052 H32 aluminum alloy to improve the joint performance than normal friction stir welding is addressed in this paper. The effects of tool rotational speed and welding speed on ultimate tensile strength by underwater and normal friction stir welding were analyzed and compared. It was observed that the tensile strength of underwater welded joints was higher than normal FSW joints except at 500 rpm. Maximum tensile strength of 208.9 MPa was obtained by underwater friction stir welding at 700 rpm tool rotational speed and welding speed of 65 mm/min. The optimum process parameters for achieving maximum tensile strength by normal FSW were compared with underwater FSW. The result showed that the ultimate tensile strength obtained by underwater FSW was about 2% greater than that of the normal FSW process. The joints with maximum tensile strength during underwater and normal welding fractured at the retreating side of the welded joint. Microstructural examination revealed that heat-affected region was not found in underwater welding. Microhardness was decreased slightly towards the stir zone. Fractography observation revealed that the welded joints exhibiting higher joint efficiency failed under ductile mode. [ABSTRACT FROM AUTHOR]

Geometry of tool pin profiles plays a significant role in deciding the quality of weld in friction stir welding process. In the present study, the effect of tool pin profile on the mechanical and metallographic characteristics of the friction stir welding on AA 5052- H32 aluminium plates was investigated. Various geometry of tool pin profile such as cylindrical tapered, hexagon tapered, pentagon tapered, square tapered, and, triangular tapered, having a constant circumscribed circle diameter were used for the study and the results are compared. Other weld parameters such as tool tilt angle, rotational speed, welding speed were kept constant based on the response from several trial runs conducted. Mechanical test results reveal that highest tensile strength and hardness value were obtained with tapered square tool pin profile and the joint failed under ductile mode. Fine equiaxed grain structure was observed at the stir zone with tapered square tool pin profile. EDS result on plate welded by tapered square tool pin profile shows that there is no β-phase (Mg2Al3) precipitate at the stir zone and therefore no sensitization of segregation as the result of FSW, thereby resists localized intergranular corrosion at the weld site. [ABSTRACT FROM AUTHOR]

In the present work, multi-objective optimization of the input welding parameters influencing the quality of weld joint of AA 5052 H32 aluminium alloy by FSW process is investigated using response surface methodology and grey relational analysis. The quality of the welded joint is measured based on the higher value of tensile strength and hardness of the joint obtained by experimentation. A central composite design technique consists of 31 sets of experiments using four factors and five levels are used. Tool pin profile, rotational speed, welding speed, and tool tilt angle are selected as the significant input parameters. Analysis of variance (ANOVA) is used to analyze the effect of each input welding parameters on the output responses. Statistical results show that the developed regression model is adequate. Optimum levels of welding parameters are finally identified using grey relation grade. Grain structure of the welded joint is examined by observing the micro and macro structures of the weld.