Syntactic Aluminum Foam from Recycled Sawing Chips
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https://doi.org/10.1007/s11837-020-04282-6 Ó 2020 The Minerals, Metals & Materials Society
ALUMINUM: RECYCLING AND CARBON / ENVIRONMENTAL FOOTPRINT
Syntactic Aluminum Foam from Recycled Sawing Chips Gy. THALMAIER
,1,3 N.A. SECHEL,1 and I. VIDA-SIMITI1,2
1.—Department of Materials Science and Technology, Technical University of Cluj-Napoca, 103105 Muncii Ave., 400641 Cluj-Napoca, Romania. 2.—Academy of Technical Sciences, 26 Dacia Boulevard, Bucharest, Romania. 3.—e-mail: [email protected]
A method for the reuse of aluminum (alloy 5754) sawing chips as a starting material for manufacturing aluminum matrix syntactic foams by powder metallurgy is described. In the tested samples, spherical Ni-superalloy hollow particles were used to increase the closed porosity of specimens up to 50 wt.%. Spark plasma sintering was used to consolidate the specimens. Only the sample with 30% hollow particles showed a clear maximum corresponding to a compression strength of 130 MPa. For all the samples, the plateau stress was over 120 MPa. The densification strain was over 40%, reaching 61% for the sample containing 30% hollow particles. All the samples showed high energy absorption capabilities and good absorption efficiency.
INTRODUCTION Environmental concerns and economic interests in today’s world make recycling of aluminum and its alloys more important than ever. Recycling scrap metal can reduce energy consumption by a factor of up to 20.1 Presently, two main directions of recycling materials are available: re-melting and solidstate methods. Solid-state recycling has some real advantages compared with liquid state recycling, at least regarding the lower energy consumption and emissions coupled with the possibility of obtaining finished or semi-finished products.2 Solid-state recycling can also significantly reduce the costs of materials and labor.3 Aluminum alloys used in industrial applications contain a significant number of alloying elements which cannot be removed cost-effectively, for thermodynamic reasons. Due to this, re-melting is more or less limited to the parts that can be cast from secondary aluminum containing significant quantities of scrap.4 According to Wan et al.5 the main solid-state techniques are based on severe plastic deformation and powder metallurgy, the latter allowing the fabrication of dense or porous parts. The present work presents a combination of these, by manufacturing syntactic foams with a recycled aluminum matrix (from alloy 5754).
(Received March 31, 2020; accepted July 5, 2020)
The aluminum alloy 5754 is a medium-strength, strain-hardening alloy, which offers extremely good resistance to both seawater corrosion and industrially polluted atmospheres. It is used in applications in industrial sectors such as marine engineering, oil and gas, chemical, and nuclear. Certain automobile frames (like van bodies) or inner body panels are also made from alloy 5754. It offers excellent weldability and good workability but only an average machinability. Aluminum matrix metallic foams (so
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