Abstract
The application of friction stir welding (FSW) to aerospace has grown rapidly due to the high efficiency and environmental friendly nature of the process. FSW is achieved by plastic flow of frictionally heated material in solid state and offers many advantages of avoiding hot cracking and limiting component distortion. Recently low density, high modulus and high strength AA2195 are used as substitute for conventional aluminum alloys since the weight saving is critical in aerospace applications. One of the problems for this alloy is weld metal porosity formation leading to hot cracking. Combination of FSW and AA2195 provides synergy effect to improve mechanical properties and weight saving of aerospace structure such as cryogenic fuel tanks for launch systems. The objective of this paper is to investigate the effect of friction stir welding speed on mechanical and microstructural properties of AA2195. The friction stir welded materials were joined with four different tool rotation speeds (350~800 rpm) and five welding speeds (120~360 mm/min), which are the two prime welding parameters in this process.
Highlights
Friction stir welding (FSW) is a solid-state joining process, in which no solidification microstructures are produced so to eliminating the brittle phases common in fusion welding of high strength aerospace aluminum alloys [1, 2]
The grain size in the advancing side is larger than that in the retreating side due to the heat input difference generated by the plastic deformation
Temperature measurement confirms the maximum temperature on advancing side is higher than that on retreating side as reported in literature [5]
Summary
Friction stir welding (FSW) is a solid-state joining process, in which no solidification microstructures are produced so to eliminating the brittle phases common in fusion welding of high strength aerospace aluminum alloys [1, 2]. Frictional heat generated by rotation and traversing of the tool due to the high normal pressure and shearing action of the shoulder along the joint line causes a softened zone of material without melting. This softened material cannot escape outside as it is under constrained extrusion by the tool shoulder. Higher tool rotation rates generate higher temperature because of higher friction heating and results in more severe mixing of material [3]. The travelling motion of the tool moves the mixed material from the front to the back of the pin. The details of the tool geometry are important and are usually restricted from publication
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