اثر پروفیل پین در بر روی نواقص همزنی اصطکاک آلیاژ آلومینیوم ۷۰۷۵ جوش داده شده Effect of Pin Profile on Defects of Friction Stir Welded 7075 Aluminum Alloy

Over the years FSW has increased significance for joining such as aluminum alloys as the heat produced during the process is not severe enough to produce the defects which are generally observed in these materials during fusion welding, Thomas et al. (1999). Rotational speed of the tool, tool traverse speed, and vertical pressure on the plates during welding are the main process parameters of FSW, Rajakumar et al. (2010). However the tool geometry which includes the geometry of the FSW tool shoulder and tool pin probe profile is also a significant characteristic which affects the weld strength. Therefore, study of the FSW process also includes the investigation and study of tool characteristics, Su et al. (2003). The effectiveness of an FSW joint is strongly affected by several tool parameters; in particular, geometrical parameters such as the height and the shape of the pin (cylindrical, trapezoidal, screwed, etc.) has a related influence on the metal flow and on the heat generation due to friction forces, Leal et al. (2008), Querin et al. (2009), Rai et al. (2011), Zhang et al. (2012). The FSW tool is a critical part of this welding process. Dawes and Thomas (1999) defined in detail the tool development approach taken at The Welding Institute and outlined the tool design aspects of the scroll shoulder concept. While there have been several studies focused on the variation of rotation and welding speeds to optimize the welding parameters and study their microstructures for aluminum alloys, limited research has been carried out on the effects of tool structure, Leal et al. (2008), Barcellona and Buffa (2004), Boz and Kurt (2004). A large majority of research conducted on the FSW process has focused specifically on visualizing the material flow around the FSW tool, Guerra et al. (2002). It is well understood that plastically deforming material is forced to flow in the direction of tool rotation from front to the rear of the FSW tool. Even though some work has been done in contemporary literature on the study of the tool shoulder and probe profile, a comparative detailed study of different basic tool features for a given material is rarely found. There is, therefore, a need to systematically investigate the effect of tool pin profile geometries on the FSW weld. In this study, the effects of various tool geometries on mechanical properties, microstructural characteristics and defects of the welded joint made from 7075 aluminum alloy were studied.