Study on the Effect of Sheet Thickness on Optimized FSW Process Parameters

Abstract

Tailor Welded Blank (TWBs) technology is an ideal approach to fabricate components in the automobile industry to meet cater weight strategies and improved corrosion resistance and crashworthiness. Now a days, TWB are mostly is fabricated using solid state joining process, namely Friction stir welding (FSW). Since, when applied to aluminium alloys, it has also been found to create welds with superior strength. In addition, this process enables to make dissimilar sheet joints with varying thickness thus producing TWBs. Therefore, FSW is a welding process, which can be suitable to obtain Al - TWBs when compared to other traditional joining methods. The predominant problem in joining of Al alloy occurs due to the existence of low melting elements which effect in a brittle film along the grain boundaries promote to hot cracks, porosity and alloy segregation. FSW helps to overcome these problems and is suitable to weld AA1100, AA6061, AA5083 and AA6082 Al alloy as issues such as phase changes, liquidation cracking, etc. are eliminated. In this investigation, two combinations, i.e. AA1100/ AA6061 and AA5083/ AA6082 were investigated in detail, using statistical techniques such as design of experiments (DoE), Response Surface Methodology (RSM) and metallographic analysis at both the macroscopic and microscopic levels. To join different thickness sheets, a tool made of super-alloy steel was used. The feasible working range of the major parameters was identified from the literature survey and through a series of welding trials, and the joints were then made according to the conditions dictated by the CCD matrix (Central Composite Rotatable Design).The results were used to develop empirical relationships for each configuration, incorporating the major factors such as tool rotational speed, axial load and welding speed. The macrostructure, microstructure and micro-hardness were analyzed for each combination. Morphology of Fracture surface was done to reveal type of failure. Confirmation test also have been conducted to check