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ORIGINAL CONTRIBUTION

Friction Stir Welding of Aluminum Sponge by Non-Porous Edge Retention A. Chandru1

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S. V. Satish1

Received: 31 March 2020 / Accepted: 5 June 2020  The Institution of Engineers (India) 2020

Abstract Aluminum sponge is obtained by gravity die casting technique using altruist die and silica sand space holders. Development of appropriate welding techniques for these metals is needed for their extensive utilization in various industries such as automobile, aerospace, and ship building. In this work, feasibilities and limitation of casted macro-porous aluminum sponge welding are analyzed. Considering the intractability in accomplishing welding by friction stir welding, the authors’ own aluminum sponge is produced by gravity die casting with the aid of altruist polymer die. Current casting methods followed by other manufacturers involve aid of high-pressure infiltrator and vacuum chamber to produce aluminum sponge. In this novel technique of producing aluminum sponge, neither vacuum assistance nor high-pressure infiltrator was needed, thereby reducing overall operating cost. Friction stir welding was performed on aluminum sponge of 8 mm thickness with cylindrical tool of shoulder diameter 25 mm and pin length 5.8 mm, tool material being high speed steel. A novel method of non-porous edge retention was considered for welding aluminum sponge to retain cellular integrity. The weld joints obtained at three different tool rotations speed of 600 rpm, 800 rpm and 1000 rpm were examined visually and with X-ray images along with few tests to determine mechanical strength. The weld joints obtained at higher speeds were free from defects, and tensile strength was few times higher to that of tensile strength of other commercially available sponge.

& A. Chandru [email protected] 1

Department of Mechanical, PESIT- Bangalore South Campus [PES University], Affiliated to Visvesvaraya Technological University, Belagavi, Bangalore 560100, Karnataka, India

Graphic Abstract Aluminum sponge welding by FSW

Keywords Aluminum sponge  Non-porous edge  Altruist die  Macro-porous  Friction stir welding

Introduction Aluminum sponge has incredible multi-functional features such as high absorption of energy, sound, vibrations, low density, and high beam stiffness. In view of their fascinating mix of properties, extensive intrigue has been appeared to create aluminum sponge for applications in packing industries [1], vehicle [2], railroads [3], aviation divisions [4] and for improved thermal management applications [5, 6]. The sponge type, i.e., closed cell and open cell, has variations in their cellular structure and compressive behavior.

123

J. Inst. Eng. India Ser. C

Open cell aluminum sponge acts as skeleton and finds its applications in energy absorption for the extension and compression of edges, heat exchangers [7]. Chemical industries use open cell foams with micro-sized pores as filters that operate in high temperature [8]. The open cell sponge can be modeled using idealized and periodic structures o