MULTIPASS FRICTION STIR PROCESSING OF Al 5086 ALLOY AND ITS CHARACTERIZATION

Abstract

There is an increasing scientific and industrial interest in the development of bulk fine-grained alloys intended for wide variety of applications. The average grain size of the . material generally plays a very significant and dominant role in deciding the mechanical and physical properties of all crystalline materials, though these properties are also influenced by several other factors. Severe plastic deformation techniques are often used to obtain fine-grained materials. Friction stir processing (FSP) is a severe plastic deformation technique developed based on the principals of friction stir welding a solid-state joining process originally developed for aluminum alloys. The review of literature shows that friction stir processing of Al 5086-0 alloy has not been carried. Further there is no evidence of large number of multipass FSP conducted on Al-Mg-Mn alloys to produce a bulk material. Further the literature does not bring out clearly whether during multipass friction stir processing, any cooling time was given between the passes or the processing were carried out in a continuous manner without any cooling time between the passes. Hence, in the present study friction stir processing of Al 5086-0 alloy has been performed by using both single pass and multipass (12 pass) FSP techniques. The two variants of multipass FSP, that is the intermittent multipass FSP (IMP) and continuous multipass FSP (CMP) were employed for processing the material. The effect of variation in processing parameters has been studied by employing four different traverse speeds of 30, 50, 80 and 110 mm/min respectively with other processing parameters kept constant.. The microstructural evolution after FSP is studied and is correlated to observed mechanical properties. The effect of variation in the tool traverse speed and the effect of two variants of FSP on the microstructure, mechanical properties and corrosion behaviour have been studied. The corrosion behaviour of the processed material has been studied using Tafel Polarisation method.