Abstract:In the present study, friction stir welding (FSW) of butt and scarf joints of Al 6063-T6 were investigated. Five different tool pin profiles (cylindrical, tapered cylindrical, square, triangular, and hexagonal) were applied for performing welding. Scarf joint, being a new joint configuration, was used and effect of pin profiles was investigated on this type of joint configuration. The effect of pin profiles on microstructure, micro-hardness, impact and tensile properties of friction stir welded Al 6063-T6 was investigated. Scanning electron and optical microscopy were employed to characterize the different zones of welded joints. A thorough discussion on correlation between mechanical properties and microstructure has been made. In addition, the formation of various defects during the FSW was discussed with the help of fractography of the fractured surfaces.
This paper focused on optimizing deep drilling parameters based on Taguchi method for minimizing surface roughness. The experiments were conducted on CNC lathe machine using solid carbide cutting tool on material AISI 321 austenitic stainless steel. Four cutting parameters such as cutting fluid, speed, feed and hole-depth, each at three levels except the cutting fluid at two levels were considered. Taguchi L 18 orthogonal array was used as design of experiment. The signal-to-noise (S/N) ratio and the analysis of variance (ANOVA) was carried out to determine which machining parameter significantly affects the surface roughness and also the percentage contribution of individual parameters. Confirmation test was conducted to ensure validity of the test result. The results revealed that the combination of factors and their levels A 2 B 3 C 2 D 1 i.e. the machining done in the presence of cutting fluid, at a speed of 500 r.p.m. with a feed of 0.04 mm/s and hole-depth of 25 mm yielded the optimum i.e. minimum surface roughness. Further, the results of ANOVA indicated that all four cutting parameters significantly affected the surface roughness with maximum contribution from speed (27.02%), followed by cutting fluid (25.10%), feed (22.99%), and hole-depth (14.29%). It is also observed that the surface finish for deep drilling process can be improved effectively through this approach.
Joining of dissimilar materials is difficult and challenging. Trend towards replacement of high density material (HDM) by low density material (LDM) is gaining importance in automotive industries. In the present work, friction stir welding (FSW) of high strength dissimilar materials i.e. aluminium alloy AA7475-T761 and stainless steel AISI 304 was conducted. The mechanical properties and microstructure of butt joint were investigated on using Taguchi L8 orthogonal array (OA). Different combinations of FSW parameters were used to obtain the maximum value of UTS. It was observed that most dominating parameter affecting UTS is tool rotational speed, contributing 42.19%, followed by traverse speed with 38.96% and shoulder diameter with 12.60%. The maximum UTS was observed 75.22% of base material AA 7475 (452MPa) under the optimum combination of parameters; tool rotational speed at 450 rpm, traverse speed 63 mm/min and shoulder diameter 14 mm. The microstructure of the resulted efficient joint shows appreciable variation in grain sizes in different zones and the micro hardness was found maximum in SZ on the retreating side.
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