A novel method for the production of metal powders without conventional atomization process A. Canakci * , T. Varol Department of Metallurgical and Materials Engineering, Engineering Faculty, Karadeniz Technical University, Trabzon, Turkey article info Article history: Received 29 April 2014 Received in revised form 19 February 2015 Accepted 27 February 2015 Available online xxx Keywords: Powder production Mechanical milling Chip recycling AA7075 abstract Fabrication of Al alloy powders from recycling chips by mechanical milling is a novel processing tech- nique. In this study, the mechanical milling was applied to the production of AA7075 powders from the recycling chips. The effect of milling time on the morphology, particle size and powder yield of the milled chips and fabricated powders was investigated. Fabricated powders were characterized by a scanning electron microscope (SEM), a Laser Particle Size Analyzer, X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS). A chip milling model based on the morphology and size of milled powders were presented. It was found that after 10 h of milling, the average particle size of the AA7075 powders was reduced to 35 mm. Results showed that 5 h of milling was the critical milling time in a change in the chip morphology (segmented shape) from powder morphology (irregular shape). The particle size of fabri- cated powders after 10 h of milling was about 286 times lower than that of initial chips. Crown Copyright © 2015 Published by Elsevier Ltd. All rights reserved. 1. Introduction Metal processing and similar industries related to manufacturing processes such as machining, surface finishing and painting have been accepted as polluting industries. The most discussed issues associated with metal processing/products, ma- chinery and automotive sectors are consumption of large amounts of raw materials and energy (Alkaya and Demirer, 2013). The waste of raw materials and energy consumption can be prevented using effective recycling methods (Hatayama et al., 2012; Koyanaka and Kobayashi, 2010). Al and its alloys have significant technological importance in automotive, defense and aircraft industries due to their light weight and high specific strength. Machining is one of the most important processes used for manufacturing semi-finished and final products of Al and Al alloys by removing the excess parts in the form of small chips. The amount of chips fabricated as a result of machining process is sufficiently large so that recycling of the machining chips is required for industrial and environmental reasons. Casting is generally supposed as a traditional method for recycling the Al and Al alloy chips. However, in the past two decades, recycling the chips by casting has been revealed to be an energy consuming, environmental destroying, and high cost process. Moreover, it was found that 46e48% of the Al chip mass became a loss during recycling using the casting process (Gronostajski et al., 2000; Samuel, 2003; Mahboubi Soufiani et al., 2010; El Aal et al., 2013). The different production methods namely centrifugal atomization (Plookphol et al., 2011), water atomization (Liu et al., 2011), chemical vapor deposition (CVD) (Jovic et al., 2006), electrolysis (Orhan and Hapçı, 2010) and mechanical milling (Varol and Canakci, 2013; Canakci et al., 2013a,b; Canakci et al., 2012) have been used to produce metal and composite powders which have superior mechanical (hardness) and physical properties (apparent density, size and shape). These metal powder production processes differ in their production rate, structure and morphology of the obtained materials and the economical aspects especially in energy consumption. However, the main goals which become prominent in high-tech applications are controlled and adjustment of particle size, structure and morphology (Liu, 2000; Kandjani et al., 2010). The atomized powders usually have a broad size distribution, which can affect not only production cost but also compact density. The amount of powder fabricated by atomization methods is very low and the use of expensive inert gas (argon or helium) is needed to prevent oxidation (Liu et al., 2011). Moreover, the conventional casting process sequence consists of four major steps: (1) Consol- idation of metal chips, (2) Melting of chip billets by using a furnace, (3) Atomization of melting metals, (4) The process of sieve analysis. However, the production of metal powders from the chips can be * Corresponding author. Tel.: þ90 462 3772927. E-mail address: aykut@ktu.edu.tr (A. Canakci). Contents lists available at ScienceDirect Journal of Cleaner Production journal homepage: www.elsevier.com/locate/jclepro http://dx.doi.org/10.1016/j.jclepro.2015.02.090 0959-6526/Crown Copyright © 2015 Published by Elsevier Ltd. All rights reserved. Journal of Cleaner Production xxx (2015) 1e8 Please cite this article in press as: Canakci, A., Varol, T., A novel method for the production of metal powders without conventional atomization process, Journal of Cleaner Production (2015), http://dx.doi.org/10.1016/j.jclepro.2015.02.090