FRICTION STIR PROCESSING & SUPERPLASTIC FORMING OF Al-5086 ALLOY

Abstract

Superplasic bulge forming of Al 5086 alloy sheet was done using friction stir 10 processing. Superplastic fonning is a technique in which a gas pressure is imposed on the superplastic sheet material, and due to this the material to form into the die cavity. the characteristics of superplastieity is low flow stress and large elongation have been utilized widely in forming processes. Friction stir processing is a tool use for grain refinement in which a rotating tool rotate on the metal and due to friction between rotating tool and metal the material soften and so that the grain refinement occur and enhance their superplasticity. Selective grain refinement is a potential application of friction stir processing which produce grain size gradient, minimize localized thinning and enhance deformation uniformity. Octagonal processing has been done by rotating the metal sheet. The metal sheet contained different layer as ntigget zone, thermo-mechanical affected zone (TMAZ) and heat affected zone. The nugget layer was used for investigation ol superplastic forming characteristics. Iwo variable process parameter of friction stir processing (FSP) was used as low heat input and high heat input. The ISP parameter of 1025 rpm and 50 nim/min is called high heat input and 720 rpm and 150 nim/min is called low heat input. Three selective condition of processing was taken as (i) Apex has high heat input and edge has low heat input, (ii) Apex has base metal and edge has low heat input and (iii) Apex has base metal and edge has high heat input. Superplastic forming characteristics as thinning factor, thickness strain, effective strain and value of m was investigated. From the results it was observed that selective grain refinement processing technique can be used to eliminate severe thickness variation and improve the integrity of the superplastic formed part