EFFECT OF CIRCULAR FRICTION STIR PROCESSING ON SUPERPLASTIC FORMABILITY OF ALUMINUM 5086 ALLOY

Abstract

Friction stir processing is a severe plastic deformation technique used for generating line grains for superplastic forming. it generates line grains in the through thickness of the sheet of Aluminium 5086 alloy. By multipass method of friction stir processing anyone is capable of producing fine grains at bulk level which is necessary for superplastic deformation. Friction stir processing was performed with two variable process parameters such as low heat input and high heat input. The FSP parameter of 1025 rpm and 70-100 mm/rn in is called high heat input and 720 rpm and 100-125mm/min is called low heat input, maintaining a tool tilt of 1/2°. MULTIPASS CIRCULAR FRICTION STIR processing was performed on a 6mm sheets with three selective conditions 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. Before performing these processing conditions it was necessary to optimize the parameters of circular friction stir processing. Processing of material was done with three different tools namely conical pin, cylindrical with hemispherical end pin, and threaded cylindrical with hemispherical end pin were used where in the third tool the shoulder has the features of impeller for better filling through flooding action and mixing of material. Superplastic forming was performed on the selectively processed plate with different aforementioned conditions. Superplastic bulge forming was performed at a range of pressure between 0.5-0.9 MPa and temperature of 500 °C, which was continued up to height of 18.88 mm. The plate with central part as base metal and Outer part is processed with 720 rpm, 110-125 mm/mm. was showing lower thickness variation from apex to edge.